Eastern extension of mineralization beyond 2025 PEA pit shell with multiple significant intercepts including 216.0 metres at 0.67% Cu Eq., including 64.1 metres at 1.10% Cu Eq., and 163.4 metres at 0.86% Cu Eq.

Highlights:

• Drilling at Red Dog accomplished three core objectives:
  • Infill drilling within the western, shallower core of the deposit has confirmed the consistency and reliability of historic drilling results.
  • Drilling in the central portion of the deposit confirmed mineralization consistent with the existing resource model and will support improved confidence in future estimates
  • Drilling in the eastern portion of the deposit demonstrated a new, high-grade zone extending past the limits of the currently modelled resource, indicating potential for resource expansion
• Selected copper-equivalent assay intercepts include:
  • RD26-29: 141.4m grading 0.97% Cu Eq. from 3.6m and 70.0m grading 0.88% Cu Eq. from 159.0m, with multiple higher grade sub-intervals
  • RD26-30: 216.0m grading 0.67% Cu Eq. from 156.0m, including 64.1m grading 1.10% Cu Eq. from 288.0m
  • RD26-33: 126.0m grading 0.89% Cu Eq. from 177.0m, including 30.0m grading 1.65% Cu Eq. from 222.0m
  • RD26-35: 163.4m grading 0.86% Cu Eq. from 165.6m, including 18.0m grading 1.58% Cu Eq. from 185.0m and 33.0m grading 1.11% Cu Eq. from 230.0m
• Additional exploration drilling commenced on May 29, 2026, with approximately 14,500 metres planned for the remainder of the 2026 program

Northisle Copper and Gold Inc. (TSX-V: NCX, OTCQX: NTCPF) (“Northisle” or the “Company”) is pleased to announce the results of drilling at the Red Dog deposit in 2025 and early 2026. A total of 8,112 metres of drilling were completed, including infill, geotechnical, and exploratory drill holes.

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Figure 1: North Island Project Showing Location of Deposits and Prospects

Drilling at Red Dog has achieved several important objectives. Infill drilling within the western, shallow core of the deposit has confirmed previous drilling results and further validated the presence of shallow, higher-grade mineralization in the deposit. Results from the central portion of the mineral resource were also consistent with the existing resource model and are expected to support increased confidence in the current resource estimate. Perhaps most significantly from an exploration perspective, drilling in the eastern portion of the deposit identified a previously unrecognized high-grade trend at depth. Historic drilling at Red Dog was largely focused on shallow mineralization, and these results highlight the potential for additional areas containing economic-grade mineralization that have not yet been incorporated into existing resource models.

As a result of the successful drilling program and the potential to improve ongoing technical work with additional mineralization from Red Dog, the Company is now incorporating the Red Dog drill results in the integrated resource estimate and subsequently into the ongoing pre-feasibility study work.

Sam Lee, President & CEO noted “Exploration at Red Dog has demonstrated very strong grades over wide intervals, both near surface and at depth, and has identified a new mineralized domain in a previously under-drilled area. We are only scratching the surface of the potential of this district-scale opportunity and will be initiating further drill programs imminently. These important results have the potential to contribute to an improved project and, as a result, we have taken the necessary steps to allow inclusion of the new Red Dog mineralization in the PFS.”

Pablo Mejia, Vice President, Exploration added “These results from Red Dog represent some of the most significant geological outcomes of Northisle’s ongoing exploration program, with drilling confirming the potential for additional mineralization below the current resource envelope and that higher-grade mineralization is not restricted to the shallow core of the deposit. Critically, the use of Scan technology (by Veracio), combined with our improved understanding of the North Island Project mineralized systems, contributed to this important outcome.”

Discussion of Drill Results

A total of 8,112 metres of drilling were completed at the Red Dog Deposit between 2025 and early 2026. The program was designed primarily to support the ongoing PFS through resource conversion, while also advancing metallurgical, geotechnical, and exploration objectives. Of the drilling completed, approximately 5,259 metres were dedicated to infill drilling, aimed at upgrading portions of the current Mineral Resource from the Inferred category to the Indicated category. In addition, 591 metres were drilled in two holes to provide material for metallurgical testing, 515 metres supported geotechnical studies, and approximately 2,338 metres targeted resource expansion and exploration opportunities. A total of 31 holes were completed during the program, with most drilling focused on the eastern portion of the deposit where additional drill density was required to improve resource confidence and support future mine planning.

The primary objective of the infill drilling program was to increase confidence in the continuity and distribution of mineralization within the current resource model. Several holes were specifically designed to validate geological interpretations and confirm grade continuity within areas already classified as Indicated resources. Notably, RD26-29 returned 141.4 metres grading 0.97% Cu Eq. from 3.6 metres, including 76.0 metres grading 1.02% Cu Eq. from 61.0 metres, while RD26-32 intersected 142.5 metres grading 0.67% Cu Eq. from 6.0 metres, including 36.0 metres grading 0.98% Cu Eq. from 19.0 metres. Both holes were drilled within the core of the deposit, where historical drilling density is highest and resources are already classified as Indicated. Core from both holes is also being used as part of the ongoing metallurgical testing program. The results demonstrate excellent continuity of both mineralization and grade distribution, providing additional confidence in the geological interpretation and resource model that underpin the ongoing PFS.

Additional drilling was completed in areas of the deposit where wider drill spacing limited resource confidence and geological interpretation. These holes were designed to test continuity between existing intercepts while reducing local gaps within the resource model. Results confirmed the presence of broad and continuous mineralization across these areas, including 47.0 metres grading 0.61% Cu Eq. from 4.5 metres, including 29.5 metres grading 0.80% Cu Eq. from 4.5 metres, in RD26-19; 109.3 metres grading 0.43% Cu Eq. from 36.0 metres, including 20.0 metres grading 0.58% Cu Eq. from 58.0 metres, in RD26-21; 55.1 metres grading 0.33% Cu Eq. from 232.9 metres in RD26-25; and 22.2 metres grading 0.94% Cu Eq. from 16.8 metres and 154.5 metres grading 0.48% Cu Eq. from 49.5 metres, including 24.9 metres grading 0.70% Cu Eq. from 51.1 metres, in RD26-38. Geotechnical holes RDGT25-01 and RDGT25-02 were also positioned to evaluate mineralization continuity while providing important geotechnical information for future engineering studies. These holes returned 51.6 metres grading 0.48% Cu Eq. from 2.4 metres, including 7.6 metres grading 0.84% Cu Eq. from 2.4 metres, in RDGT25-01 and 109.0 metres grading 0.38% Cu Eq. from 52.0 metres, including 10.0 metres grading 0.84% Cu Eq. from 73.0 metres, in RDGT25-02. Together, these results further support the continuity of mineralization throughout the Red Dog resource area and provide additional confidence for future resource modelling and mine planning.

Beyond resource conversion, several holes were designed to test the down-dip continuity of mineralization below the current resource envelope in the eastern portion of the deposit, where the recent infill drilling had identified higher-grade mineralization at depth. The identification and follow-up of these higher-grade zones were enhanced by the use of Veracio's Scan technology, which provided near real-time geochemical information and helped guide geological interpretations during the program. Results from RD26-30, RD26-33, RD26-35, RD26-36 and RD26-37 confirmed the presence of a broad and continuous mineralized trend extending below areas targeted by much of the historical drilling. Highlights include 216.0 metres grading 0.67% Cu Eq. from 156.0 metres, including 64.1 metres grading 1.10% Cu Eq. from 288.0 metres, in RD26-30; 126.0 metres grading 0.89% Cu Eq. from 177.0 metres, including 30.0 metres grading 1.65% Cu Eq. from 222.0 metres, in RD26-33; 163.4 metres grading 0.86% Cu Eq. from 165.6 metres, including 18.0 metres grading 1.58% Cu Eq. from 185.0 metres and 33.0 metres grading 1.11% Cu Eq. from 230.0 metres, in RD26-35; 102.3 metres grading 0.49% Cu Eq. from 211.7 metres, including 40.4 metres grading 1.06% Cu Eq. from 317.0 metres and 13.4 metres grading 1.68% Cu Eq. from 344.0 metres, in RD26-36; and 109.0 metres grading 0.57% Cu Eq. from 362.0 metres, including 29.5 metres grading 0.91% Cu Eq. from 392.0 metres, in RD26-37.

These results represent one of the most significant geological outcomes of the program. Historical drilling at Red Dog largely focused on the shallower portions of the system, with limited drilling evaluating the continuity of mineralization at depth. The new drilling confirms that mineralization extends well below the historically defined resource envelope and that higher-grade mineralization is not restricted to the shallow core of the deposit. The consistency of both broad mineralized intervals and higher-grade zones across multiple drill holes suggests the presence of an emerging eastern high-grade trend and highlights the potential for additional mineralized domains beyond those currently incorporated into resource models.

Exploration drilling completed outside the principal infill areas yielded mixed results. Holes RD25-03 and RD26-39 were designed to evaluate the lateral and vertical extent of mineralization beyond the current resource envelope and provided important geological information for future targeting. While RD26-39 intersected 39.0 metres grading 0.46% Cu Eq. from 276.0 metres, including 18.0 metres grading 0.65% Cu Eq. from 294.0 metres, the hole did not identify a significant extension comparable to those encountered within the central and eastern portions of the deposit. Similarly, several shallow holes drilled in the northeastern portion of the deposit (RD26-17, RD26-18, RD26-22 and RD26-26) returned limited mineralization, suggesting that the shallow northeastern sector may be less prospective than other portions of the system. In contrast, RD26-31 intersected 19.5 metres grading 0.27% Cu Eq. from 5.4 metres, demonstrating that shallow mineralization remains locally developed within the north-central portion of the deposit and identifying an area that may warrant additional follow-up drilling to better define its extent and continuity.

The results of the 2025-2026 drilling program provide strong support for both resource conversion and future growth opportunities at Red Dog. The program successfully achieved its primary objective of increasing confidence through infill drilling while simultaneously identifying a deeper high-grade mineralized trend in the eastern portion of the deposit. With mineralization now outlined over approximately 800 metres of strike length and more than 400 metres of vertical extent, the continuity of broad mineralized intervals and higher-grade zones supports the potential for future resource growth and suggests that the mineralized footprint of the deposit remains open for expansion at depth and toward the east. These results continue to improve the Company’s understanding of the Red Dog system and reinforce its potential as an important component of the North Island Project.

Note on equivalent calculation for Red Dog:

Copper equivalent grade is determined by calculating total contained metal value per tonne, adjusted for recoveries, if known, dividing by the copper price, and then dividing the resultant number of pounds of copper by 2,204.6.Gold equivalent grade is determined by calculating total contained metal value/tonne, adjusted for recoveries, if known, dividing by the gold price, and then multiplying the resultant number of troy ounces of gold by 31.103. Analyzed metal equivalent calculations are reported for illustrative purposes and consider 80% recovery for gold, 80% recovery for copper, and assume 80% recoveries for Molybdenum and Rhenium as metallurgical testing has not yet been completed for these two elements on material from the Northwest Expo deposit.

Gold and copper equivalent calculations based on the following metal prices, which were used in the Company’s 2025 Preliminary Economic Assessment for the North Island Project: Cu = US$4.20/lb, Au = US$2,150/oz, Mo = US$21/lb, Re = US$1,950/kg. Intervals were selected based on continuous intercepts with Cu grade above 0.1% Cu or Au grade above 0.1g/t Au. Totals may not add due to rounding.

Intervals are drill intersections and not necessarily true widths. True widths cannot be provided at this time due to the uncertainty in the geometry of the mineralization. Drill intersections have been selected and composites calculated independently by Northisle. The locations and distances highlighted on all maps in this news release are approximate.

Note on Red Dog holes:
Holes RD25-04 through RD25-11 were drilled in the West Goodspeed area and their results were previously reported in Northisle's news release dated November 17, 2025. Hole RD26-34 was abandoned due to challenging ground conditions before reaching its target depth. Hole RD26-23 was terminated early following a reinterpretation of the geological model and target priorities based on information available at the time, allowing the program to focus on higher-priority targets elsewhere within the deposit.

Figure 1 shows a map of the overall North Island Project including existing deposits, key prospects, and the focus area of this release.

Figure 2 shows the location of the drill holes announced in this press release in context with previous drilling in the Red Dog area, while Figure 3 presents a long-section highlighting results from this release, illustrating the distribution of recent drilling and mineralized intervals along the deposit.

Exploration and Development Milestones

Key project milestones for 2026 include the following:

• COMPLETED – Updated Preliminary Economic Assessment on North Island Project
• COMPLETED – C$39.5 million financing
• COMPLETED – BC Hydro Conceptual Review of Interconnection
• COMPLETED – Team additions and enhancements to support growth
• COMPLETED – Commencement of expanded baseline study program to support EA Readiness
• COMPLETED – Largest ever field program at North Island Project with 20,297 metres and 58 holes drilled
• COMPLETED – Confirmed mineralization at West Goodspeed over 1.2km strike
• COMPLETED – Identified copper-gold mineralization at the Cougar Target
• COMPLETED – C$115 million financing to advance the North Island Project
• COMPLETED – Infill drilling results at Northwest Expo, extending strike and highlighting higher-grade zones
• COMPLETED – Commence extension drilling in Northwest Corridor; initial results expected in H2 2026
• COMPLETED – Initiate early engagement on mine waste storage area (ahead of schedule)
• COMPLETED – Drilling results at Red Dog, confirming additional higher-grade mineralization extending below the existing resource envelope
• Q2/Q3 2026 – Initial metallurgical test results for the North Island PFS
• Q2/Q3 2026 – Integrated resource update for the North Island Project
• Q3 2026 – Initiate drilling at regional exploration targets
• Q4 2026 – Results from drilling at regional exploration targets
• Q4 2026 / Q1 2027 – North Island PFS results announced
• H2 2026 – Initial Project Description filed
• H2 2026 – Commence BC Hydro System Impact Study
• Ongoing – Continued positive engagement with indigenous rightsholders and local stakeholders

Additional Technical Details

Logging, Sampling and Assaying Procedures and QA/QC

The diamond drill core logging and sampling program was carried out under a rigorous quality assurance / quality control (QA/QC) program. Drill intersections in this release are typically HQ to 150 metres and NQ thereafter to the end of holes. After drilling, core was logged for geology, structure, and geotechnical characteristics utilizing MX Deposit —core logging software, then marked for sampling and photographed on site. The cores for analyses were marked for sampling based on geological intervals with individual samples of 3-metre length or less. Drill core was cut lengthwise in half with a core saw. Half-core was sent for assays reported in this news release.

A minimum of +9.33% assay standards or blanks and +4.64% core duplicates are included in the sample stream as a quality control measure and are reviewed after analyses are received. Standards and Pulps Blanks were obtained from CDN Resource Laboratories, Langley, British Columbia. Coarse Blanks were obtained from unmineralized course bagged limestone landscaping rock. Standards and blanks in 2025 and 2026 drill results to date have been approved as acceptable. Duplicate samples sourced from both pulp and coarse rejects as well as quarter-core field duplicates add to the long-term estimates of precision for assay data on the project and precision for drill results reported is deemed to be within acceptable levels.

Samples were sent to the MSALABS in Langley, British Columbia, where the samples were dried, then crushed, split and a 250-gram (g) split was pulverized to 85% passing -200 mesh (-75 micrometres (µm)) size pulps. Clean crush material was passed through the crusher, and clean silica was pulverized between each sample. The pulps were analyzed for gold by fire assay fusion of 50 g of the 250 g split. Total gold content was determined by digesting the silver doré bead from the fusion and then analysing by AA (MSA Code FAS-121). All samples were also analyzed for multiple elements by taking a 0.25 g of the 250 g split which was heated in HNO3, HClO4 and HF to fuming and taken to dryness. The residue was dissolved in HCl and then analyzed utilizing ICP-MS (MSA Code IMS-230). Any copper analysis exceeding 1% had the pulp re-analyzed using the “Ore grade” ICP-ES finish to constrain copper content up to 40% (MSA Code ICF-6Cu). Any sulphur analysis from this latter analysis with a value greater than 10% was reanalyzed utilizing a Leco sulfur analyzer. Iron and Tungsten accelerators are added to the sample and a stream of oxygen is passed over the sample in the induction furnace. As the sample is heated, sulfur dioxide released from the sample is measured by an IR detection system and the Total Sulphur content is determined. (MSA Code SPM-210). MSALABS (Langley) is an independent, international ISO/IEC 17025:2005 accredited laboratory.

Pulps and rejects of holes with significant assay intervals are stored at West Coast Mineral Storage. The remaining split core is indexed and stored at the Company’s logging and office facility in Port Hardy, BC.

Drill Results in this news release are length weighted averages.

Qualified Persons and Data Verification

Dr. Pablo Mejia Herrera, P.Geo., Vice President Exploration of Northisle, and a Qualified Person as defined by National Instrument 43-101 Standards of Disclosure for Mineral Projects, has reviewed and approved the scientific and technical disclosure contained in this news release. Dr. Mejia Herrera has verified the data disclosed, including the sampling, analytical and test data underlying the disclosure, through multiple visits to drill sites, oversight of sample preparation protocols, and review of the QA/QC procedures applied to analytical results received from MSALABS.

About Northisle

Northisle Copper and Gold Inc. is a Vancouver-based company whose vision is to become Canada’s leading sustainable mineral resource company for the future. Northisle, through its 100% owned subsidiary North Island Mining Corp., owns the North Island Project, which is one of the most promising copper and gold porphyry projects in Canada. The North Island Project is located near Port Hardy, British Columbia on a more than 34,000-hectare block of mineral titles 100% owned by Northisle on a belt stretching 50 kilometres northwest from the now closed Island Copper Mine operated by BHP Billiton. Since 2021, the Company has discovered two significant deposits, expanded resources, demonstrated the economic potential of the project, and is now focused on the development of this compelling project while exploring within this highly prospective land package.

Northisle respectfully acknowledges that our North Island Project is located within the territories of Quatsino First Nation, Kwakiutl First Nation, and Tlatlasikwala First Nation. We are committed to collaborating with First Nations to build authentic, mutually beneficial relationships.

For more information on Northisle please visit the Company’s website at www.northisle.ca.

Cautionary Statements regarding Forward-Looking Information

Certain information in this news release constitutes forward-looking statements under applicable securities law. Any statements that are contained in this news release that are not statements of historical fact may be deemed to be forward-looking statements. Forward-looking statements are often identified by terms such as “may”, “should”, “anticipate”, “expect”, “intend” and similar expressions. Forward-looking statements in this news release include, but are not limited to: plans and expectations regarding the 2026 exploration program; plans and expectations regarding future project development; timing of key catalysts; planned activities, including further drilling, at the North Island Project; anticipated impact of drilling results from Red Dog and other targets on Mineral Resource Estimates; the Company’s anticipated exploration activities; and the Company’s plans for advancement of the North Island Project. Forward-looking statements necessarily involve known and unknown risks, including, without limitation, the Company’s ability to implement its business strategies; risks associated with mineral exploration and production; risks associated with general economic conditions; adverse industry events; stakeholder engagement; marketing and transportation costs; loss of markets; volatility of commodity prices; inability to access sufficient capital from internal and external sources, and/or inability to access sufficient capital on favourable terms; industry and government regulation; changes in legislation, income tax and regulatory matters; competition; currency and interest rate fluctuations; and other risks. Readers are cautioned that the foregoing list is not exhaustive.

Readers are further cautioned not to place undue reliance on forward-looking statements as there can be no assurance that the plans, intentions, or expectations upon which they are placed will occur. Such information, although considered reasonable by management at the time of preparation, may prove to be incorrect and actual results may differ materially from those anticipated. Forward-looking statements contained in this news release are expressly qualified by this cautionary statement.

The forward-looking statements contained in this news release represent the expectations of management of Northisle as of the date of this news release, and, accordingly, are subject to change after such date. Northisle does not undertake any obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise, except as expressly required by applicable securities law.

Neither the TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this news release.

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We are only scratching the surface of the potential of this district-scale opportunity and will be initiating further drill programs imminently.