After Japan's attack on Pearl Harbor pushed America officially into the war 7 December 1941, "Niblack" continued to escort North Atlantic convoys to Reykjavík, Iceland, Derry, Northern Ireland, and Greenock, Scotland. In July 1942 she was transferred to the Caribbean for temporary duty at the height of the U-boat campaign there, resuming northern duty in August. In November 1942, she escorted the first support convoy to Casablanca after the Allied landings on the Moroccan Coast. The ship then performed coastal convoy escort duty until departing early in May 1943 for Mers-el-Kébir, Algeria.