Frank J. O'Connor, 74, a former labor leader and a labor adviser with the Agency for International Development, died Friday at Washington Adventist Hospital. He had cancer.

Mr. O'Connor joined the foreign assistance program in the mid-1950s. He served in Greece, the Phillippines Turkey, and Liberia as an adviser to the governments of those countries until his retirement from AID in 1969. He also worked at AID headquarters here.

Mr. O'Connor, who was born in Washington, had been a stone and marble mason in his earlier years. Active in union affairs, he eventually headed Local 2 of the Stone and Marble Masons Union.

From 1948 until 1956, he was executive secretary of the Washington Building Trades Council. In 1952, as a member of the Democratic State Central Committee for the District of Columbia, he was a delegate to the Democratic National Convention.

Mr. O'Connor at one time had been active in the Knights of Columbus.

Survivors include his wife, Hannah, of Bowie, where the family had lived for the past 10 years; three children, Richard, of Baltimore, Kathleen, of Greenbelt, and Sharon Pritzl, of Bowie; a brother, Daniel, of Houston; a sister, Mary Thomas of Arlington, 12 grandchildren and three great-grandchildren.