The deal comes a year after Julien led the team to the 2011 Stanley Cup championship — its first in 39 years.
In five seasons with Boston, Julien has a record of 228-132-50. He is third in franchise history with 410 games coached and fourth in wins, trailing Art Ross, Milt Schmidt and Don Cherry.
Under Julien, the Bruins have never missed the playoffs. They are 36-27 in the post-season since he arrived in 2007.
He was the NHL's coach of the year in 2009.
Julien also coached the Montreal Canadiens and New Jersey Devils. In all, he has a 347-218-14 record.