Krejci, 25, was in the final year of his contract that will pay him $4 million this season.
In a news conference Thursday afternoon, Bruins general manager Peter Chiarelli confirmed an ESPN.com report that the deal is worth an average of $5.25 million per year. Chiarelli also praised the Czech center for his talent and vision on the ice.
"In looking at what David has done for the Bruins, a very important contributor has really developed his two-way game and he's obviously a very good offensive player," Chiarelli said. "We saw him shine in the playoffs last year and we saw what the loss of him meant to us the year before in the playoffs. He's done everything we've asked and more.
"David's biggest asset is his head. He sees the ice so well. He makes plays, he uses the players around him."
After a slow start to the season, Krejci has picked it up as the Bruins have gotten hot, winning 12 of their past 13 games. The first-line center had just one point in seven games in October but bounced back with nine points in 12 November games, including a goal and two assists in Wednesday night's 6-3 win against Toronto.
Chiarelli pointed out that the new contract was actually signed Wednesday afternoon in his hotel room prior to the game.
"I'd like to think that we had a little bit to do with his great night," Chiarelli said, joking about Krejci's three-point outing against the Maple Leafs.
Krejci acknowledged that the contract talks and the fact he did not know where they stood weighed on his mind the more he struggled.
"I know that my agent and Peter talked in the summer. I didn't know what was going on but honestly it was on my mind a little bit especially when things weren't going my way at the beginning of the season. It got me thinking a lot," Krejci said. "But then we got the deal done and I'm happy to be here for more years and now I can just focus on hockey."
Krejci has spent his entire career in the Bruins' organization after being taken in the second round of the 2004 draft. He's been with the big club since the 2006-07 season. He has tied for the Bruins' team lead in points in each of the past two seasons (52 in 2009-10 and 62 in 2010-11). He was especially valuable last postseason, when he led the Bruins with 23 points en route to the Stanley Cup.
Krejci pointed to that Cup run and the strong possibility that the Bruins could add more during the next three seasons as a reason he elected to sign an extension.
"We won the Cup last year, and I feel this team can do it again and I want to be part of it," Krejci said. "It was a great experience, and I hope that I'll win it one more time. I feel like I have a really good chance here with this team. That was the biggest reason."
James Murphy covers the Bruins for ESPNBoston.com. Information from ESPN.com's Pierre LeBrun was used in this report.