Stephon Castle's 33 points included 11 in the fourth quarter and rookie Dylan Harper added 27 points and 10 rebounds off the bench as the Spurs roared home to take a 2-1 series lead.
They had dropped game two at home after Wembanyama was injured in a hard fall.
The 22-year-old French star cheered from the bench as his teammates turned the tide in Portland, where they will try to build on their series lead on Sunday.