Valiant was built in 1929 as the private yacht Vara by the Herreshoff Manufacturing Company at Bristol, Rhode Island.

PC-509 was assigned to the Panama Canal Zone, where she was based throughout her naval career, and tasked with escorting convoys in the Gulf of Mexico and the Caribbean Sea.

From February 1942 through April 1943, she escorted convoys according to a varied itinerary that included visits to Guantanamo Bay and Havana in Cuba; Jacksonville, Miami, and Key West in Florida; and Charleston, South Carolina.

On 15 July 1943, she was classified as a coastal patrol yacht (PYc), renamed USS Valiant, and redesignated PYc-51.

Between convoys, she conducted routine patrols and participated in searches for German submarines, although there is no record of her ever seeing combat.