For Chicago, it was their third consecutive win and ended a season that began with the team setting an NHL record by going on a remarkable run in which they earned at least one point in their first 24 games.
"It was one of those seasons we were saying, we're almost charmed the way we started the season and the way we ended," Chicago coach Joel Quenneville said. "Nobody saw that one coming either way.
"A lot of great things in between, some great challenges in this play-off series or this play-off round, and then let alone the other three (series).
"But it was one of those seasons, fairytale ending and an amazing season."
While it was a fairytale finish for the Blackhawks, it was a nightmare end to the season for Boston.
Bruins fans had believed the best-of-seven series was headed back to Chicago for a winner-take-all showdown after Milan Lucic put the Bruins ahead 2-1 with about eight minutes to play.
But with netminder Corey Crawford pulled in favour of an extra attacker, Bryan Bickell tied the game with a tap in from the side of net moments before Dave Bolland sealed the Cup for Chicago in front of a stunned Boston crowd.
While it was anything but hockey weather with temperatures soaring to 35 degrees Celsius in Boston, the city was caught in the grips of hockey fever with the Bruins facing a must-win game to force a winner-take-all showdown.
With the Stanley Cup in the TD Center and the champagne on ice, it was all hands on deck as Chicago captain Jonathan Toews and Bruins top faceoff man Patrice Bergeron returned after missing the end of previous game with undisclosed injuries.
Boston had snatched the early lead when Chris Kelly scored the only goal of the opening period but the Blackhawks dominated the rest of the first Stanley Cup final between Original Six teams since 1979.
Toews, who won the Conn Smythe Trophy for the most valuable player when Chicago last won the Stanley Cup in 2010, tied the game with a goal in the second period.
Boston regained the lead briefly in the final period when Milan Lucic scored but the celebrations were cut short by Chicago's stunning rally.
"Well it was probably the toughest (end) for sure when you know you're a little bit over a minute left and you feel that you've got a chance to get to Game Seven and then those two goals go in quickly," said Boston coach Claude Julien.
"But at the same time, it's one of those things where you look at who you played against, and that Chicago ... they're deep. They got stronger as the series went on, and they're a great hockey club."
Chicago's Patrick Kane, who led his team with 19 points during the postseason, was awarded the Conn Smythe Trophy as the most valuable player of the play-offs.
"I think there's something about our core," said Kane, who was also on Chicago's Stanley Cup-winning team in 2010.
"Hopefully we can stay together a long time, because that's two Cups in four years, and we seem to only be getting better and better as players as time goes on here.
"It's unbelievable to be in this situation."