The 33-year-old South African replaces his former boss Michael Foley, who was sacked in June a few days after the Australian Rugby Union took control of the franchise to ensure its survival.
"This opportunity is an amazing privilege," Wessels said in a news release.
"Not only because I love the game of rugby but also because I am so passionate about the Western Force and the people of Perth.
"What we want to do going forward is develop a fantastic learning environment that people want to be a part of and that embraces the unique pioneering spirit that Western Australians will be proud of."
The Force have never qualified for the playoffs in the 11 seasons since their debut in 2006.
Wessels took charge of the side after Foley's dismissal for the last three matches of last season but was unable to lead them to a victory and they finished third from bottom of the 18-team standings.
Located a five-hour flight from the east coast heartland of Australian rugby, the Force have struggled to retain top players and Wessels' appointment came on a day when likely future Wallaby Kyle Godwin departed for the ACT Brumbies.
Zimbabwe-born centre Godwin, who is in the Australia squad for the Rugby Championship, signed a two-year deal to join the Canberra-based Brumbies after playing 52 matches for the Force since his debut as a teenager in 2012.
