Williams made back-to-back 3-pointers to begin the extra period and finished with 22 points, LeBron James scored 36, and the Cavaliers beat the Raptors 126-118 on Friday night.
"Road wins continue to establish momentum going down the stretch," James said. "We've played two really good games the last two nights."
Cleveland, which made 10 3-pointers in Thursday's 108-88 victory over the Celtics, got 11 more against Toronto, including six from Williams. The point guard made four 3s in the Cavs' big fourth quarter in Boston.
"It's a deadly weapon for our team," James said. "Last night and also tonight, we shot the ball extremely well from the perimeter."
Cavaliers coach Mike Brown praised his team for using quick passes to get open looks from outside.
"Any time you advance the ball on the pass instead of the dribble, you're going to beat players down the floor," Brown said. "When we threw the ball ahead, we were able to get great looks because they weren't all the way back."
Antawn Jamison scored 22 points and Delonte West added 15 for Cleveland, which won its third straight. Anderson Varejao had 11 points and eight rebounds before fouling out with 2:12 left in the fourth quarter.
Toronto had the ball with 13 seconds left in regulation but Turkoglu settled for a 3-pointer that missed wide.
"I was feeling good and I wanted to take it, but in that situation I could have taken a better shot instead," Turkoglu said.
The Cavaliers have won 15 of their past 18 meetings with the Raptors.
Jamison topped 20 for the first time in five games with the Cavaliers and said he's becoming more comfortable on offense.
"I'm starting to understand when guys want me to cut and when guys want me to spot up," Jamison said. "There's still a little bit of fine-tuning we've got to do."
Varejao started in place of Shaquille O'Neal, who left Thursday's game with a sprained right thumb. O'Neal is scheduled to have an MRI on Saturday.
Cleveland led 105-98 with 3:39 to go, but Bargnani hit a step-back jumper, Turkoglu made a reverse layup and Wright made a pair from the line to cut it to 105-104 with 2:12 remaining.
James ended the run with two free throws, but Turkoglu tied it with a 3-pointer from the wing, then gave Toronto a 109-107 lead with a follow dunk on Jack's missed layup with 50 seconds left.
James tied it with a layup, Jack made two free throws and James answered with another driving layup, making it 111-all with 13 seconds remaining.
Toronto gave the ball to Turkoglu, but he missed a 3-pointer from the wing, giving Cleveland a second for a final shot. After a timeout, the Cavaliers gave the ball to Anthony Parker, but he missed a 3 at the buzzer.
The Raptors never challenged in the extra session, shooting 1 for 8.
James went down wincing after he was kneed in the thigh in a collision with DeMar DeRozan in the first half. He fell heavily again in the second half, landing on the ball.
"Not a good day for me," James said. "It still hurts. Its one of those things that won't go away for a while. It'll be a few days before I'll be 100 percent again."
James stayed in the game after the first incident and later threw down a driving dunk, forced a steal and made one free throw, then hit a 3-pointer after Cleveland grabbed the rebound on his missed second shot.
The spurt put the Cavaliers up 10, and they led by as many as 12 before Toronto rallied, cutting it to 33-30 after one quarter.
The Raptors kept it close through the second, and Wright's 3-pointer with 3.9 seconds left in the half tied it at 60 heading into the break.
Cleveland recalled forward Darnell Jackson from the Erie BayHawks earlier Friday. ... O'Neal ate dinner in the media lounge while watching Olympic speed skating on TV. ... Actress Elisha Cuthbert and boyfriend Dion Phaneuf attended the game, as did actor John Malkovich and Canadian sprinter Donovan Bailey.