Hanns Hatt studied biology, chemistry and human medicine at the LMU Munich, where he received his doctorate in zoology in 1976. In 1981 Hatt received his license to practice medicine and was promoted to Dr. med. PhD and habilitation in physiology at the medical faculty (Klinikum rechts der Isar) of the Technical University of Munich, where he was appointed full professor of physiology at the medical faculty in 1991.

Hanns Hatt has been a professor at the Faculty of Biology and holder of the Chair of Cell Physiology at the Ruhr University Bochum since 1992.

In 2009, Hatt was elected as the successor to Manfred J. M. Neumann from the Institute for International Economic Policy at the University of Bonn as President of the North Rhine-Westphalian Academy of Sciences and Arts for the 2010 to 2012 term of office. In 2012 he was elected again until 2016. Wolfgang Löwer was his successor. In 2012 he was elected a member (matriculation no. 7486) of the Leopoldina. From 2013 he was Vice President and since 2015 he has been President of the Union of German Academies of Sciences.