The 29-year-old has also been appointed the team's new captain ahead of the 2014-15 campaign, replacing Chris Bell.
The England international has made nearly 140 appearances for Wasps during two separate spells at Adams Park.
"Wasps is so much a part of my life, having played here for nine seasons in total," Haskell told the club's official website. "I have a lot to thank the club's coaches and support staff for, in helping me to get back into the England setup last season.
"The squad is the most competitive it has been in years, with a number of internationals arriving, as well as exciting young lads who are keen to make an impact."
Wasps play their first match of the season on September 6 when they face Saracens.