John M. O'Connell Jr., 72, a retired official of the U.S. Maritime Administration who came to Washington in 1933 as secretary to his father, a newly elected Democratic congressman from Rhode Island, died of cancer Saturday at a hospital in Lexington, Ky.

A longtime resident of Chevy Chase, Mr. O'Connell had lived in Lexington since his marriage in 1979 to the former Alice Cheatham.

After spending six years as secretary and administrative assistant to his father, Mr. O'Connell joined the Agriculture Adjustment Administration in 1939. During the 1940s, he was an information analyst with the Office of Price Administration, a consultant to the Economic Cooperation Administration and a Congressional liaison aide with the Commerce Department.

From 1951 to 1953, he was a special assistant to the U.S. deputy maritime administrator. He then spent eight years as an employe of the House of Representatives before returning to the Maritime Administration as its assistant secretary in 1961. He held that post until retiring in 1970.

Mr. O'Connell was a native of Rhode Island and a graduate of Providence College. He earned a law degree at Georgetown University.

His first wife, Marguirette, died in 1977.

In addition to his wife, of Lexington, Mr. O'Connell's survivors include two daughters, Anne Marie Giancoli of Glendale, Md., and Michele Abraham of Silver Spring; a stepson, William B. Martin of Louisville, and eight grandchildren.