Naval Reserve (USNR) as Seaman second class at Minneapolis, Minnesota, on 14 January 1941 and was appointed Aviation Cadet at Pensacola, Florida, on 20 March 1941.

[1] On 20 February 1942, he intercepted a Japanese bomber, determinedly pursued it through clouds and rain, and assisted in shooting it down despite heavy machine gun and cannon fire.

After trial runs and tests, final outfitting, and shakedown, Sellstrom departed Bermuda on 3 December 1943 for the east coast, arriving at Charleston Navy Yard on the 6th.

On 31 January, Task Force 63 stood into the Straits of Gibraltar, turned over the escort of their convoy to British control, and set course to Casablanca, French Morocco.

Sellstrom was relieved of the convoy in Chesapeake Bay on 22 February and proceeded to New York, mooring at the Brooklyn Navy Yard the next day.

As flagship of Escort Division 23, Sellstrom guided the New York section of the convoy into the swept channel on 1 May and patrolled the area until all merchant vessels had pilots on board.

She successfully escorted sections of convoy TCU-35 into the Clyde and Loch Ewe, Scotland, and into Lough Foyle, Northern Ireland, on 21 and 22 August.

The destroyer escort accompanied six more Atlantic convoys, delivering merchantmen to the ports of Belfast, Northern Ireland; Liverpool, Plymouth, Southampton, and Birkenhead, England; and Le Havre, France.

Sellstrom's operations consisted of routine patrols and serving as a guard ship vessel for flights over the northern Japanese island chain.

From December 1945 through February 1946, Sellstrom operated in the postwar Pacific, visiting such ports as Qingdao, China; Jinsen, Korea; and Pearl Harbor.

On 1 November 1955, Sellstrom was taken out of the Atlantic Reserve Fleet and was brought to the Brooklyn Navy Yard for overhaul and conversion to a radar picket escort ship.

After shakedown training at Guantanamo Bay and post-shakedown overhaul, Sellstrom began carrying out assignments on the radar picket lines and as an ocean weather station.