Following the Marshalls operation, "Halsey Powell" departed Pearl Harbor on 30 May for rehearsals in connection with the upcoming Marianas invasions. She sortied with the assault force from Eniwetok on 11 June, and as troops stormed ashore on Saipan four days later she took up fire-support station off the beaches, and was an effective force in victory. In addition to screening, radar picket duties, and fire support for ground forces, "Halsey Powell" sank a net tender, a cargo ship and numerous small craft in the lagoon with her guns.