Nickerson was subsequently ordered to the Far East, where meanwhile the Korean War broke out after the Korean People's Army (KPA) invaded South Korea. He was ordered to Tokyo and attached as advisor on Marine Corps Matters to the General Headquarters, Far East Command under General of the Armies, Douglas MacArthur. He was subsequently attached as liaison officer to the 1st Marine Regiment, 1st Marine Division and took part in the Battle of Inchon and subsequent recapture of Seoul in September 1950. Nickerson distinguished himself during the crossing of Han River, when he exposed himself to the KPA's direct fire to move from one company to another to obtain information vital to the successful continuation of the drive against the KPA. He received the Silver Star for his gallantry in action.