In the Battle of the Java Sea on 1 March 1942, "Ashigara" shared in the sinking of the cruiser and the destroyer . On 10 March 1942, she became flagship for the Second Southern Expeditionary Fleet, and led the invasion of Christmas Island on 26 May 1942. She became flagship of the Southwest Area Fleet from 10 April 1942, and returned to Sasebo Naval Arsenal for a refit and repairs in June. She returned to Makassar in July to resume her position as flagship of the Second Southern Expeditionary Fleet, but for the rest of the year was primarily engaged as a rapid troop transport based out of Surabaya. She was dry-docked and repaired at Seletar Naval Base in Singapore at the end of the year.