Pastrnak became the first player since Claude Giroux in 2012 and just the sixth overall to have a three-goal, three-assist playoff game. At 21 years, 324 days, he surpassed Wayne Gretzky (22 years, 81 days) as the youngest player to have a six-point game in the postseason.
Pastrnak called it a "huge honor" to have bested Gretzky in the record books.
"Six points in a Stanley Cup playoff game with a hat trick," Bruins coach Bruce Cassidy said. "That's special."
Pastrnak has been special in both games of the team's first-round series, as the Czech Republic native registered three points in a Game 1 victory. His nine combined points tie him with Phil Esposito (1969) for the most points accumulated in the first two games of a postseason in NHL history.
"A lot of people in Boston already know how good he is," said teammate Patrice Bergeron, who had four assists of his own in Game 2. "I think people on the outside are getting to know."
The Bruins, who lead the series 2-0, will take their show on the road, as Game 3 is Monday in Toronto.