When the Japanese attacked Pearl Harbor, "Hopkins" was at Johnston Island for war maneuvers, but immediately headed back to Hawaii. She continued patrol of the Hawaiian Sea Frontier, with a short break for overhaul in the States, until late summer 1942, when she joined the invasion fleet bound for Guadalcanal. As America's first offensive of the Pacific war began 7 August, "Hopkins" swept the transport area and covered the landings on Tulagi. During a heavy enemy air attack 9 August, she shot down two enemy planes, and in the following months, "Hopkins" escorted transports, swept mines, and carried badly needed supplies to Guadalcanal.