Jason Chimera added two assists for the Capitals, while Matt Bradley and Andrew Gordon also scored. Dany Sabourin started in net and stopped all 12 shots he saw in a little more than 32 minutes. Braden Holtby took over from there and made 13 saves to grab the win.
Boston heads to Europe for its final two preseason games, playing in Belfast, Ireland on Saturday before traveling to the Czech Republic on October 5. The Bruins open the regular season in Prague with a home-and-home series against the Coyotes (October 9-10).