Ashton was born and raised in Homestead, Iowa, where he lived on a farm with his parents, older sister, Tausha, and twin brother, Michael. To finance the cost of his education in bio-chemical engineering at the University of Iowa, Ashton worked as a cereal dust sweeper at the General Mills plant in Cedar Rapids as well as taking on many other jobs to pay for college. After being discovered by a local model/talent scout, he moved to New York to pursue acting.
Since his arrival in New York in August 1997, Ashton's determination has landed him roles in a National Pizza Hut commercial, an NYU student film entitled "Distance," and a CK Jeans campaign. Other film credits include, Coming Soon opposite Gaby Hoffman, Reindeer Games opposite Ben Affleck and Gary Sinise.
Ashton starred on the hit U.S comedy That 70s Show, as the loveable goof Kelso. He also stars in Down To You which stars Freddie Prinze Jr and Julia Stiles, and Texas Rangers opposite James Van Der Beek and Dylan McDermott. In 2000 Ashton starred in Dude, Where's My Car?
In 2007, Aston's long running series Punk'd ended. However, in 2011 it resumed it's ninth season with Ashton as executive producer.