Karsten Filsø is a Trained social educator. After a number of years as a department manager at the Schuberts Minde Treatment Home in Ringkøbing, in 2002 Karsten and a colleague set up a residence in No near Ringkøbing for children and young people who are placed outside their own homes. In 2016, Karsten divested the residence.
Karsten Has been a local politician since 1998, elected for SF - first in Ulfborg-Vemb Municipal Council and since the amalgamation of municipalities in Holstebro City Council in 2007.