John R. Cocker, 66, retired executive vice president of Riggs National Bank, died of cancer Thursday at Arlington Hospital. He lived in Arlington and Madison, Va.

He joined Riggs as a mailroom messenger in 1936. He later headed the bank's general ledger and bookkeeping departments and was elected assistant cashier in 1948. He became a vice president of the bank in 1959, then was named the bank's senior vice president and cashier in 1971. He was elected executive vice president in 1976. He retired in July 1980.

He was a former chairman of the audit and control section of the D.C. Bankers Association and a past secretary of the D.C. Clearing House Association.

He had been a treasurer of the Dominion Hills Civic Association and had served on the financial committee of Westover Baptist Church.

Mr. Cocker was a native of Paterson, N.J., and had worked for the New York Title and Mortgage Co. before coming here in the mid-1930s. He attended Southeastern University and was a graduate of the American Institute of Banking, and took graduate banking courses at Rutgers University.

Survivors include his wife, Doris Miller Cocker of Arlington and Madison, Va.; two sons, Robert, also of Arlington, and Dr. Wesley Coker of Nashville, Tenn,; his mother, Elsie M. Cocker of Arlington; a brother, Roland M., of North Carolina, and five grandchildren.