Montréal serves on MARLANT missions protecting Canada's sovereignty in the Atlantic and Arctic Oceans and enforcing Canadian laws in its territorial sea and Exclusive Economic Zone.

The ship has also been deployed on missions throughout the Atlantic and to the Indian Ocean; specifically the Persian Gulf and Arabian Sea on anti-terrorism operations.

[6][7] To reflect the changing long-term strategy of the Navy during the 1980s and 1990s, the Halifax-class frigates were designed as general purpose warships with particular focus on anti-submarine capabilities.

[8] As built the Halifax-class vessels deployed the CH-124 Sea King helicopter, which acted in concert with shipboard sensors to seek out and destroy submarines at long distances from the ships.

[8] As built, the anti-shipping role is supported by the RGM-84 Harpoon Block 1C surface-to-surface missile, mounted in two quadruple launch tubes at the main deck level between the funnel and the helicopter hangar.

[6][8] For anti-aircraft self-defence the ships are armed with the Sea Sparrow vertical launch surface-to-air missile in two Mk 48 Mod 0 eight-cell launchers placed to port and starboard of the funnel.

[8] A Raytheon/General Dynamics Phalanx Mark 15 Mod 21 Close-In Weapon System (CIWS) is mounted on top of the helicopter hangar for "last-ditch" defence against targets that evade the Sea Sparrow.

Further improvements, such as modifying the vessel to accommodate the new Sikorsky CH-148 Cyclone helicopter and satellite links will be done separately from the main Frigate Equipment Life Extension (FELEX) program.

The existing 57 mm Mk 2 guns were upgraded to the Mk 3 standard and the Harpoon missiles were improved to Block II levels, the Phalanx was upgraded to Block 1B and the obsolete Sea Sparrow system was replaced by the Evolved Sea Sparrow Missile.

[4] In January 1995 Montréal joined the NATO mission in the Adriatic Sea enforcing the United Nations blockade of Yugoslavia.

[4] In July 2000, the American merchant ship GTS Katie refused to bring its Canadian military cargo into port, claiming unpaid fees.

On 30 July, the Canadian Forces sent the destroyer HMCS Athabaskan to maintain contact with the rogue ship and deployed Montréal the following day.

[17] The warship had remained longer than usual in theatre due to a crash of a CH-124 Sea King aboard her replacement, the destroyer HMCS Iroquois.

On 3 July 2011, as part of their national Canadian tour, the Duke and Duchess of Cambridge embarked on the vessel which conveyed them from Montréal to Quebec City.

After further Sea Acceptance Trials and Work Ups, Montréal assumed Normal Readiness on 9 March 2015, being the fifth post-refit frigate to achieve this milestone.

[citation needed] In late 2015, Montréal deployed for a large NATO naval exercise, Joint Warrior.

[35] On 26 March 2023, the frigate and the supply ship Asterix left Halifax on a deployment to the South China Sea and the Indo-Pacific region.

[36] On 3 June, the People's Liberation Army Navy warship Suzhou cut across the bow of USS Chung-Hoon while the American destroyer was transiting the Taiwan Strait together with Montréal; the closest point of approach was 140 metres (150 yd).