[4] Calgary serves on MARPAC missions protecting Canada's sovereignty in the Pacific Ocean and enforcing Canadian laws in its territorial sea and exclusive economic zone.

The Halifax-class frigates were ordered by the Canadian Forces in 1977 as a replacement for the St. Laurent, Restigouche, Mackenzie, and Annapolis classes of destroyer escorts, which were all tasked with anti-submarine warfare.

[5] In July 1983, the federal government approved the budget for the design and construction of the first batch of six new frigates of which Calgary was a part, out of twelve that were eventually built.

[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.

[6][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.

[7] Two Thales Nederland (formerly Signaal) SPG-503 (STIR 1.8) fire control radars are installed one on the bridge-top and one on a raised platform on the forward end of the helicopter hangar.

[6] On 10 July 1995, Calgary was sent to the Persian Gulf as part of the force used to enforce sanctions on Iraq, her mission lasting until December of that year.

The following year the frigate redeployed to the Persian Gulf, once again as part of the group enforcing sanctions against Iraq, replacing sister ship Regina.

[16] Calgary, accompanied by Winnipeg, Yellowknife and Brandon, departed in October 2014 to take part in San Francisco Fleet Week and the Task Group Exercise (TGEX) with the US Navy in American coastal waters.

The Royal Canadian Navy deployed four of its Orca-class patrol vessels and one CP-140A Aurora aircraft to search for signs of oil spill, but found none.

[20][21] On 30 July 2018, Calgary departed Esquimalt for a five-month deployment to the Pacific Ocean taking part in naval exercises with Japan, South Korea, New Zealand and Australia.

[25] On 23 April 2021, while operating off the coast of Oman as part of CTF 150, Calgary intercepted a vessel suspected of smuggling and recovered 1,286 kg (2,835 lb) of heroin.