"Cowichan" was armed with a single quick-firing (QF) /40 caliber Mk IV gun mounted forward. This was later replaced with a 12-pounder () 12 cwt HA gun. For anti-aircraft purposes, the minesweeper was equipped with one QF 2-pounder Mark VIII and two single-mounted QF 20 mm Oerlikon guns. The 2-pounder gun was later replaced with a powered twin 20 mm Oerlikon mount. As a convoy escort, "Cowichan" was deployed with 40 depth charges launched from two depth charge throwers and four chutes.