Ottawa serves on MARPAC missions protecting Canada's sovereignty in the Pacific Ocean and enforcing Canadian laws in its territorial sea and Exclusive Economic Zone.

[5][6] To reflect the changing long term strategy of the Navy during the 1980s and 1990s, the Halifax-class frigates were designed as a general purpose warship with particular focus on anti-submarine capabilities.

[7] 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.

[7] 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.

[5][7] 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.

[7] 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.

[10] After commissioning, Ottawa, accompanied by the Kingston-class coastal defence vessel Nanaimo, transferred to the West Coast, departing Halifax, Nova Scotia on 16 November 1996.

[10] On 6 June 2011, Ottawa began a four-and-a-half-month training deployment and goodwill tour in the Pacific which included port visits to Australia, South Korea, Singapore, and Japan.

[11] Ottawa participated with the Royal Australian Navy and United States Seventh Fleet in the multi-lateral naval exercise Operation Talisman Saber 2011 from 11 to 26 July 2011.

It is a biannual, multi-national maritime exercise held off the coast of Hawaii and is designed to improve interoperability and understanding between military forces from nations with an interest in the Pacific Rim, increasing stability in the region.

[19] Ottawa and sister ship Winnipeg sailed from Esquimalt on 6 March 2017 for six-month deployment visiting several nations around the Pacific, including Malaysia, India, China and Japan among others, returning on 8 August.

[23] On 6 August, Ottawa sailed for a six-month deployment to Asian-Pacific waters which included enforcing United Nations sanctions against North Korea.

[29] In October 2024, Ottawa departed CFB Esquimalt for a deployment of Asian waters as Canada's contribution to the multi-national Operation Horizon.

[30] On 26 December, Ottawa completed a mission to conduct anti-smuggling operations related to North Korea from late November to mid-December.