On 23 September 1944, Sims entered the Boston Navy Yard for conversion into a Charles Lawrence-class high speed transport.

After transiting the Panama Canal, and a brief shakedown period at San Diego, the transport arrived at Pearl Harbor on 20 February.

A week later, the transport stood out of Leyte Gulf as part of Task Unit 51.13.16, bound for the invasion of Okinawa.

Both planes, hit by anti-aircraft fire, crashed into the water on her port side with a violent explosion that lifted and shook the entire ship.

Sims departed Okinawa on 27 May with a convoy which she escorted to Saipan before continuing on to Leyte for damage repairs.

On 14 August, Sims rendezvoused at sea with the Tokyo Bay Occupation Force south of Japan.

The ship landed a group of British Marines and Royal Navy personnel at the Yokosuka Naval Base on 30 August.

The transport disembarked 208 passengers at San Diego, California, on 17 December 1945, and continued to New York for pre-inactivation overhaul.