Then ordered to New York City for conversion to an attack transport at the Atlantic Basin Iron Works yard, she was decommissioned on 8 July, converted, and recommissioned on 18 December 1944.

After shakedown in Chesapeake Bay, Riverside proceeded to Davisville, Rhode Island; loaded men and equipment of the 81st Construction Battalion; and departed for the Pacific Ocean.

In mid-April, she returned to Hawaii; conducted amphibious landing exercises through May; tested equipment and trained personnel in cargo handling in June; and in mid-June got underway on another Hawaii-California run.

At the end of the month, she shifted from San Pedro, California, to Portland, Oregon, for availability, and in early July steamed west with reinforcements for Okinawa.

From Korea she returned to Okinawa and toward the end of October joined the "Operation Magic Carpet" fleet to bring American troops back to the United States.