Father was concertmaster and violinist David McCallum Sr.; a black & white photograph from the mid-1960's of David, Sr. and David, Jr. was used during one episode of NCIS (2003). The photo can be seen in Victoria's (Ducky's mother's) bedroom in NCIS: The Meat Puzzle (2005).
Lives on Long Island, New York
His first wife, Jill Ireland, met her second husband, Charles Bronson, during the filming of The Great Escape (1963).
Has appeared in episodes of three different series with Robert Vaughn: The Man from U.N.C.L.E. (1964), Please Don't Eat the Daisies (1965) and The A-Team (1983).
Of the three original stars of The Man from U.N.C.L.E. (1964), he is the only one who never appeared on the spin-off series The Girl from U.N.C.L.E. (1966).