Fehn was born in Des Moines and raised in Ankeny, Iowa, just north of Des Moines. Fehn joined the band around April 1997, replacing percussionist Greg Welts, who was forced out of Slipknot after the band due to personal conflicts with drummer Joey Jordison which stemmed from Welts dating Jordison's sister.
As well as lending his percussion talents to the band, Fehn has also sung backing vocals on a number of songs Slipknot has both recorded and performed live. Fehn describes himself as a "big fan of the band" and says of Slipknot, "the world needed something like this."
Prior to joining Slipknot in 1997, Fehn was close friends with Slipknot's percussionist Shawn Crahan. Shortly after his request was made, Fehn was given an offer to play custom percussion in the band. Fehn was then given a rough demo that contained all of Slipknot's songs. Fehn then tried out on percussion and was subsequently made part of Slipknot.
In a recent interview with Face Culture, Fehn said that the band members gave him a hard time in his early years with the band. In April 2010, it was announced that Fehn will be playing bass for the band, Will Haven.
Chris Fehn's masks all have the same overall design, worn over a bondage hood. His first mask for the bands self-titled era was white. For the Iowa era he changed to a tanned leather mask. One of his more popular masks was from the Vol. 3 Subliminal verses which had a red face. His most recent mask for All Hope Is Gone has a color similar to the Iowa era mask. Fehn's mask design is most likely based on those worn by doctors during the Black Plague, where the nose was filled with herbs to 'protect' the doctor from inhaling the fumes of death. In particular Chris' mask resembles a version of Pantalone's phallic-nosed mask.
A fourth idea of the origin of the mask is the Pinocchio character.
Backstage at Slipknot's second Ozzfest show, Fehn expanded on the mask to a local interviewer, saying, "This mask reflects my comic personality.