Robert C. Jones, Sr., 81, a retired investment securities broker who was a member of the New York Stock Exchange, died Friday at Suburban Hospital in Bethesda after a stroke. He lived at Knollwood in Potomac and Lyford Cay in the Bahamas.

He formed Robert C. Jones and Co. in 1930 in Washington. Later it had offices also in Alexandria, Silver Spring and Bethesda.

The firm became Jones, Kreeger and Co. about 1950. Mr. Jones retired about 1965.

He was born in Washington and graduated from Oxon Hill High School. After serving as an Army captain in France in World War I, he entered the securities business here in 1919.

Mr. Jones was recalled to active duty in the Army Air Forces in World War II, when he reached the rank of colonel.

He had been active in the growth of Suburban Hospital. He was a member of the Society of the Cincinnati.

His first wife, the former Virginia C. Lewis, died in 1959.

He is survived by his seconed wife, the former Jille Romney, of Knollwood and Lyford Cay; two sons, Robert C. Jr., of Washington, and Kenneth P., of Miami, Fla.; a daughter, Virginia A. Dykhuizen of Potomac, and five grandchildren.