Heinrichs taught at Giessen from 1968 to 1977, when he went to Harvard University as a visiting lecturer, and in 1978 took up a permanent position there.[1] In 1980 he married Alma Giese, an independent scholar and translator from Arabic. In 1989 he became a co-editor of the new edition of the Encyclopaedia of Islam, for which he also wrote fifty articles himself.[2] In 1996 he succeeded Muhsin Mahdi as the James Richard Jewett Professor of Arabic at Harvard.[1] A Festschrift was published in 2008.[2]