Ramstad was Republican member of the Minnesota State Senate from 1981 to 1990 before entering the U.S. Congress. He served in the 102nd, 103rd, 104th, 105th, 106th, 107th, 108th, 109th, and 110th congresses, beginning on January 3, 1991. He first defeated former Minneapolis city councilman Lou DeMars in the 1990 election.

Ramstad was a member of the United States House of Representatives from 1991 until 2009, representing Minnesota’s 3rd congressional district, one of eight congressional districts in Minnesota. On September 17, 2007 Ramstad announced he would not seek reelection in 2008.

Ramstad considered ending discrimination against those suffering from mental health and addiction problems a major part of his legacy, and worked under both Republican and Democratic majorities to pass a Mental Health Parity Bill. Mental Health Parity was eventually passed and signed into law in December, 2008.

Ramstad is currently a resident fellow at the Harvard Institute of Politics where he is leading a study group titled The Policy and Politics of Addiction.