The Bruins climbed back from deficits of 2-0 and 4-3 to beat the Penguins for the ninth straight time. Pittsburgh's last win against Boston came on Nov. 1, 2003, and its last win in Boston was Feb. 8, 2003.
Hannu Toivonen recovered from a shaky first two periods to record his first win in three months for the Bruins. Toivonen, whose last win came on Oct. 19 against Calgary, allowed four goals on 21 shots through two periods before saving 12 shots in the third to force overtime. He then had two more saves in overtime and turned back 3-of-4 shots in the shootout to set up Kessel's winner.
Glen Murray, Brad Stuart and Marco Sturm also scored for Boston.
Evgeni Malkin scored twice and Jordan Staal and Ryan Malone each added goals for the Penguins.