© NBC Universal / Syfy
TV Line reports that the former Beverly Hills, 90210 star will play a character named Chris Weekly in four episodes.
An intelligent but anti-social marine biologist, Weekly will arrive in the town of Haven with a mysterious affliction.
Priestley currently plays the lead role in sitcom Call Me Fitz and has previously appeared in episodes of Scoundrels, My Name Is Earl and Medium.
He has also signed up to direct an episode of Haven, which was picked up for a second run last October.
The new season is expected to premiere this summer on Syfy.
