He joins Joe Launchbury, Elliot Daly, Rob Miller, Ashley Johnson, Tom Cruse and Alex Rieder who have all previously this season committed their long-term futures to the black-and-gold.
Bassett joined Wasps from Bedford Blues in 2013 after beginning his rugby career with Ampthill.
He won England under 20 honours in 2012 after ending a prolific campaign as the Championship’s top try-scorer with 14.
Wasps Director of rugby Dai Young added: “I’m very happy that Josh has signed a new deal here at Wasps.
“As his try-scoring record shows, he’s been a real asset for the club since he arrived.
“Bass is also a hard worker, and at 25 there is still plenty of improvement potential in him.
“He is also a well-liked member of the group who brings plenty of energy about the place; we’re delighted to have him on board for the long-term.