At the time of the attack on Pearl Harbor on 7 December 1941, "Mutsuki" was the flagship of Destroyer Division 30 under Destroyer Squadron 6 of the 4th Fleet. She sortied from Kwajalein on 8 December as part of the Wake Island invasion force, carrying an advance landing party of the Japanese Special Naval Landing Forces (SNLF). Early on the morning of 11 December, the American garrison repulsed the first landing attempts by the SNLF, which was supported by the light cruisers , , and and the destroyers , , , "Mutsuki", , and , two old vessels converted to patrol boats ("Patrol Boat No. 32" and "Patrol Boat No. 33"), and two troop transports containing 450 SNLF troops. After taking heavy losses (including "Kisaragi" and "Hayate"), the Japanese force withdrew before landing. This was the first Japanese defeat of the war, and also the only occasion in World War II when an amphibious assault was repulsed by shore-based guns. "Mutsuki" returned on 23 December with the second Wake Island invasion force, and again carried a SNLF advance landing party before returning to Kwajalein.