On 30 June 1943, the New Georgia campaign began with the U.S. landings on New Georgia, Rendova, and other islands in the central Solomons. Ro-106 departed Rabaul that day to begin her fourth war patrol, assigned a patrol area off Rendova. On 18 July 1943, she torpedoed the United States Navy tank landing ship in the Blanche Channel off New Georgia at . The torpedo blew LST-342 in half; her stern section sank immediately, but her bow section remained afloat and was towed to Purvis Bay, beached on Gavutu, and stripped of usable materials and equipment. Meanwhile, Ro-106 concluded her patrol with her return to Rabaul on 21 July 1943.
