Ullenhag was chairman for the Liberal Youth of Sweden between 1997 and 1999 and a member of the Riksdag between 2002 and 2006, and again from 2009 to 2010.
Ullenhag menjadi ketua Pemuda Liberal Swedia antara 1997 dan 1999 dan Anggota Riksdag antara 2002 dan 2006, dan kembali dari 2009 sampai 2010.