The "Chuck" star will play a man, Mulder (David Duchovny) turns to for information during an investigation, said The Hollywood Reporter.
The actor first announced his casting via Twitter over the weekend.
"Keeping my fit on running in Vancouver, as I dip my acting self into this world for a sweet brief moment. @thexfiles," he wrote.
"The X-Files" revival includes the return of original series stars Duchovny, Gillian Anderson, Mitch Pileggi, Annabeth Gish and William B Davis.
The limited series will begin on January 24 on Fox.
