Pacioretty also ran his point streak to nine games (16 points; 10 goals, six assists).
Chandler Stephenson had three assists, and Robin Lehner made 23 saves for Vegas (17-11-0), which has won five of its past six.
"I liked our defensive game," Golden Knights coach Peter DeBoer said. "It was a good start to a tough road trip in a tough building tonight. I liked our game. [Part of our offensive success] is we're getting healthy. We're starting to score on the power play fairly regularly, which is adding about a goal a night, which we didn't have early in the year."
Patrice Bergeron scored, and Jeremy Swayman made 21 saves for Boston (14-9-2), which had won two in a row.
"You're going to have tough breaks sometimes, but it's all about how you respond," Swayman said. "Everything is a learning experience, and some of the best things you can learn are from the great failures. I think there are a lot of things tonight I can learn from."