Given hull classification symbol SS-78 in July 1920, R-1 was ordered to the Pacific Ocean on 11 April 1921, transited the Panama Canal in late May, and arrived on 30 June at her new base, San Pedro, California.

Although limited in cruising range, the R-boats operating out of Ordnance Island, Bermuda continued their patrols through the Kriegsmarine submarine offensive of early 1942.

On that patrol line, some 300 miles (480 km) northeast of Bermuda, R-1 (under command of Lieutenant James D. Grant) sighted and fired four torpedoes at the surfaced U-boat U-582, and was credited with sinking the German submarine, although U-582 was in fact undamaged.

Through November 1944 she rotated between Bermuda and New London and, at the latter, in December underwent an extensive conversion to enable her to participate in the development of ASW equipment and tactics.

Returning to the Thames River base on 29 June, she headed south again on 7 July and at mid-month reported for duty with the Fleet Sonar School at Key West, Florida, where she served for the remainder of her career.