Ullendorff was educated at the Graues Kloster in Berlin, the Hebrew University in Jerusalem, and the University of Oxford in Oxford.

He was previously Reader in Semitic Languages at the University of St. Andrews, Professor of Semitic Languages at the University of Manchester, and Professor of Ethiopic at the University of Oxford.

He is now Professor Emeritus at the School of Oriental and African Studies (SOAS) in London, where he was Professor of Ethiopian Studies and then of Semitic Languages.