He was the Federal Minister for Transport, Building and Urban Development in the grand coalition cabinet led by Angela Merkel between 2005 and 2009.

Since 2014, he has been the State Minister of Economy, Science and the Digital Society in the government of Thuringia's Minister-President Bodo Ramelow.

[6] Also during his tenure as Germany's transport minister, Tiefensee announced the little-known architect Francesco Stella as the winner of a competition to find an architectural design for the controversial reconstruction of the Berlin Stadtschloss in 2008.

Tiefensee resigned from his seat in parliament when he became State Minister of Economy, Science and the Digital Society in the government of Thuringia's Minister-President Bodo Ramelow in 2014.

[8] In May 2020, Tiefensee announced that he would not stand in the next Thuringian state election but instead resign from active politics by the end of the parliamentary term.