After launching his acting career in Ireland and England, Mulhare moved to the United States, memorably replacing Rex Harrison as Henry Higgins in My Fair Lady (1957–60), for which he toured both nationally and overseas. He played the ghost in the TV series The Ghost and Mrs. Muir (1968–70), appeared in the TV movie Gidget Grows Up (1969), and acted in the TV shows Streets of San Francisco (1972) and Knight Rider (1982–86).
