In 1905, he became extraordinary professor in Leipzig, in 1910 extraordinary professor at the Technischen Hochschule München, where he became professor in 1915. In 1920 he followed Paul Stäckel as professor at the Universität Heidelberg, where he became rector in 1926 and dean of the faculty of mathematics and natural science in 1923/1924 as well as in 1928/1929. In 1935 he asked for retirement due to political pressure of the national socialists because of Liebmann's Jewish ancestry.[3] He and his colleague Arthur Rosenthal were boycotted in his faculty. He spent his last years in Munich.
In 1913 he married his first wife Natalie Liebmann, née Kraus († 1924), who was the daughter of Karl Kraus, professor of agricultural science in Munich. After the death of his first wife he married Helene Ehlers. He had four children.
Siegfried Gottwald, Hans J. Ilgauds, Karl H. Schlote (Hrsg.): Lexikon bedeutender Mathematiker. Bibliographisches Institut, Leipzig 1990, ISBN3-323-00319-5.
Gabriele Dörflinger: Heinrich Liebmann – Mathematiker. In: Badische Biographien, Neue Folge, Band 6 (2011), S. 258–259. (Manuskript.)
Dorothee Mußgnug: Die vertriebenen Heidelberger Dozenten : zur Geschichte der Ruprecht-Karls-Universität nach 1933. Heidelberg 1988
Heinrich Liebmann: Die Notwendigkeit der Freiheit in der Mathematik (Leipziger Antrittsvorlesung) in: Herbert Beckert, Walter PurkertLeipziger mathematische Antrittsvorlesungen. Auswahl aus den Jahren 1869-1922, B. G. Teubner, Leipzig 1987 (mit Biografie)