After military service Lammert studied political science, sociology, modern history and social economics at the university of Bochum and the University of Oxford (England) from 1969 to 1975. He graduated in 1972 but carried on studying to get a doctorate in social sciences in 1975.
Although he has worked as a lecturer, Lammert became a member of the Bochum City Council in 1975. He was elected to the Bundestag in 1980, and has been a member ever since.
Lammert was a Vice-President of the Bundestag from October 2002 to 18 October 2005, when he became President.
In 2005, he was elected the President of the Bundestag, the German parliament. Even though the President of the Bundesrat acts as deputy for the Federal President, according to the German order of precedence, Lammert, as President of the Bundestag, is Germany's highest ranking official after the Federal President.