Lamers became a member of the Christian Democratic Union and its youth division, the Junge Union (JU), in 1975. From 1981 to 1986 he acted as deputy state chairman of the Junge Union Baden-Württemberg under its State Chairman Günther Oettinger, who later became Minister-President of the state of Baden-Württemberg and is currently serving as European Commissioner for Energy. Since 2003, Lamers is honorary chairman of the CDU division of Heidelberg after being its chairman from 1985 to 2003 and a member of the Municipal Council of Heidelberg 1987 to 1995.
Lamers was elected Deputy Chairman of the Defence Committee of the Bundestag in 2005 and is still holding this office. He is a member of the NATO Parliamentary Assembly since 1998 and was elected its president in Warsaw on 16 November 2010.[2] Lamers also acted as President of the Atlantic Treaty Association from 2008 to 2014, succeeding Robert E. Hunter, who held the office from 2003 to 2008.
In March 2019, Lamers announced that he would not stand in the 2021 federal elections and resign from active politics by the end of the parliamentary term.[3]