After fitting out, undergoing post-commissioning alterations, and completing acceptance trials, Andres proceeded to Bermuda, whence she carried out her shakedown from 12 April to 3 May.

Andres then steered various courses and speeds, picking up men from the water; these proved to be the 31 survivors (28 merchant seamen and three members of the Navy armed guard detachment) of USAT Oneida, which, after straggling from a coastal convoy en route from New York to Guantánamo Bay, had foundered and sunk in bad weather at 0213 on 4 May, some 70 miles northeast of Cape Charles.

Completing the rescue effort at 1950, and ascertaining from the survivors than no additional boats and rafts had gotten clear of Oneida before she had gone down, Andres then resumed her voyage to Philadelphia.

She then operated principally in the Florida Straits area as a school ship at the Submarine Chaser Training School (SCTS), Miami, Florida, indoctrinating student officers and nucleus crews, and interspersed this training with periodic overhauls at the Charleston Navy Yard, South Carolina, (19–29 March, 25 June – 1 July, and 16–26 October 1944).

After refresher training out of Casco Bay, Maine, the destroyer escort then proceeded to Norfolk, Virginia, where she was assigned to Task Force 64.

News of the German surrender reached her on 7 May 1945 shortly after she had conducted antisubmarine warfare exercises off Mers-El-Kebir in company with Edgar G. Chase, John M. Bermingham, and Doris, and had concluded a "rescue of survivors drill."