Following shakedown, which lasted until 4 April 1940 including a cruise to the West Indies and Rio de Janeiro, Stack proceeded to the west coast and thence to Pearl Harbor where she operated with the Pacific Fleet until June 1941. She then returned to the east coast for an overhaul at the Philadelphia Navy Yard. Stack began patrolling off Bermuda late in November with the Neutrality Patrol. After the United States entered World War II, Stack continued to patrol in the Caribbean until 22 December when she was assigned to escort Wasp (CV-7) from Bermuda to Norfolk.
On the 28th, she sailed from Norfolk as screen for Long Island (CVE-1). She arrived at Casco Bay, Maine, two days later. She refueled and got underway for Argentia in the screen for Long Island and Philadelphia (CL-41). Arriving in Argentina on New Year's Day 1942, she was assigned to patrol duty. On January 15th, she and Ericsson each picked up two survivors from SS Dayrose, which had been torpedoed the night before off Cape Race. (continued)