Lässig worked as a research assistant at the Department of Saxon history of the Technical University of Dresden. She was a Habilitation Fellow of the Deutsche Forschungsgemeinschaft and 2002-2006 Research Fellow at the German Historical Institute Washington (DC). She completed in 2003 a study on the "gentrification of Jews in Germany". Her habilitation thesis, the "Jewish way into the middle class" was later published and she received the 2004 Habilitation prize of the German Historians Association.
Between 2006 and 2015 Simone Lässig was director of the Georg Eckert Institute for International Textbook Research and Professor of Modern History at the Technical University of Braunschweig. From October 2009 to June 2010 she was a visiting professor at St Antony's College of University of Oxford.
From 2015 until 2025 Simone Lässig was the director of the German Historical Institute in Washington. Her research interests include the social - and cultural history of the 19th and 20th centuries, particularly Jewish history, religion and religiosity, entrepreneurs history, European history and issues of history teaching. In October 2025, she returned to her position as Professor of Modern History at the Technical University of Braunschweig.
