Encarnacion hit a pair of two-run homers for Toronto as the Blue Jays took a big lead early and held on to beat the slumping Boston Red Sox 7-4 on Tuesday night.
Encarnacion has hit nine of his 11 homers this season this month, which has 10 days left.
"He is pretty good," Toronto manager John Gibbons said. "But even last year I think he got off to a slow start somewhat. It's not going to hold him down. It's usually just a matter of time."
Melky Cabrera and Erik Kratz also homered for the Blue Jays, who won for the sixth time in eight games and extended Boston's losing streak to five straight.
J.A. Happ (3-1) struck out six in the first three innings and picked up his third win in four starts since joining the rotation.
"I felt like it was going to be a good night," Happ said. "I was trying to attack the zone and I felt my location was good."
Jonny Gomes hit a two-run homer for Boston. The losing streak is the longest for the Red Sox since 2012.
Casey Janssen picked up his fourth save, with a rocky ninth inning. Dustin Pedroia and Shane Victorino led off the ninth with consecutive singles. David Ortiz nearly tied it with a long fly ball that drifted foul, and then struck out. Janssen got Mike Napoli to ground into a double play to end it.
"If you get to the ninth inning with the lead and you've got your closer in there, you've just got to let it ride. You try to get to that point and the game's on the line," Gibbons said.
Encarnacion hit a two-run homer in the third and Kratz added a solo shot in the fourth off Felix Doubront (2-4), who left the game after Jose Reyes and Cabrera opened the fifth with back-to-back doubles. The Red Sox said Doubront complained of fatigue in his left shoulder.
"This is the first night he's felt this to this extent. His stuff was diminishing even in the early innings, particularly between the fourth and fifth," Boston manager John Farrell said.
Edward Mujica replaced Doubront and struck out Jose Bautista, but Encarnacion followed with a towering shot to left for his second two-run homer of the night and Toronto led 6-0.
Boston scored twice in the fifth, and then Cabrera added a solo shot to left in the sixth.
Happ started the sixth but was pulled after Gomes' two-run homer cut Toronto's lead to 7-4. He allowed four runs on seven hits and struck out six.
Napoli led off the sixth with a single and Gomes followed with a homer that bounced off the top of the Green Monster. Crew chief Gary Cederstrom needed only about 30 seconds to review the video before confirming it was a home run, pulling Boston within 7-4.
Boston is on its longest skid since losing the last eight games of the 2012 season. The Red Sox were 3 for 14 with runners in scoring position and left nine on base.
"We're in a little rut right now but we'll find a way to get out of it," Pedroia said.
Boston loaded the bases with one out in the fourth, but third baseman Brett Lawrie helped get Happ out of the jam.
Lawrie lunged at a line drive by Xander Bogaerts that was headed for left field. The ball bounced out of his glove when he landed, but Lawrie quickly grabbed it, tagged third for the force out and threw it to Kratz to double-up David Ortiz at the plate.
"Lawrie made an unbelievable play," Happ said. "I don't know if anybody else makes that play. Really athletic. That was huge."
Doubront allowed five runs on five hits, striking out two and walking three.
Notes: Toronto RHP Drew Hutchison (2-3) is scheduled to face Boston right-hander Clay Buchholz (2-3). ... Encarnacion hit multiple homers for the third time this season and 14th in his career. ... Red Sox manager John Farrell said before the game that Boston had re-signed veteran SS Stephen Drew, a member of last year's World Series championship club who turned down a $14.1 million offer from Boston and become a free agent. ... Toronto LHP Rob Rasmussen made his major league debut when he came in from the bullpen with one out in the seventh.