Retired Rear Adm. John G. Johns, 77, a submarine and destroyer officer who served in World War II and the Korean conflict, died Sunday in Buszards Bay, Mass., after a heart attack. He lived in Rossmeor Leisure World.

His last assignment before his retirement in 1955 wa on the board of inspection and surveys under the chief of naval operations here.

Adm. Johns was attached to a submarine squadron at Pearl Harbour when it was attacked by the Japanese on Dec. 7, 1941. Later in World War II, he commanded a submarine squadron. He commanded a destroyer squandron sent to Korea during the conflict there.

He was born in Delaware and graduated in 1925 from the Naval Academy at Annapolis, where he later was a chemistry instructor between assignments at sea. He also graduated from the Navy Submarine School at New London, Conn., and the Industrial College of the Armed Forces here.

Adm. Johns moved to Chevy Chase in the early 1650s when he became chief of priorities and control at the Defense Department.

After retiring from military service, he managed the Washington engineering office of the Enterprise Engine and Machinery Co., manufacturers of diesel engines. He also was a manufacturer's representative for several other firms before his second retirement in 1968.

He is survived by his wife, Dorothy Nelson, of the home; a daughter, Pamela J. Barry, of Acton, Mass., and two grandchildren.