The Yankees began the inaugural London Series with a six-run first inning at London Stadium. All-Star second baseman DJ LeMahieu led off with a single and scored on first baseman Luke Voit's RBI double.
Shortstop Didi Gregorius and designated hitter Edwin Encarnacion added doubles of their own to extend the Yankees' early lead. Center fielder Aaron Hicks forced Boston starting pitcher Rick Porcello out of the game with the first home run in London Series history.
Boston quickly rallied back for a six-run first inning of their own. Rookie Michael Chavis punctuated the inning with his 13th home run of the year, a three-run shot off veteran pitcher Masahiro Tanaka.
Porcello and Tanaka were each lifted midway through the first inning. That marked the first time in the Red Sox-Yankees rivalry (since 1908) that neither starting pitcher completed a full inning.
New York regained the lead on Brett Gardner's two-run home run in the third inning. Gardner brought another run home with a bases-loaded walk in the fourth inning.
LeMaheiu, who finished 4-for-6, cleared the bases with a three-run double. Outfielder Aaron Judge hit a two-run home run to close the Yankees' second six-run frame.
The two teams combined for 30 runs on 37 hits. Chad Green earned the win for the Yankees and veteran Steven Wright took the loss for Boston.
The game drew 59,659 fans, the largest crowd to see a Major League game since September 2003.
"The atmosphere here was crazy," Gregorius said. "It's what you want to see. It was like a soccer match, but with baseball."
LeMaheiu became the first Yankees leadoff hitter with four hits and five RBIs in a game since Johnny Damon on June 17, 2006.
Boston had a six-run eighth inning before reliever Zack Britton induced two groundouts. Yankees closer Aroldis Chapman worked around a one-out single in a scoreless ninth.
The first-place Yankees have a 7 1/2 game lead over the Tampa Bay Rays in the AL East Division.