Bayern's win at Werder Bremen earlier in the day meant Jurgen Klopp's side required three points to make sure of claiming the 'salad bowl' for the second time in two years and they duly delivered thanks to goals from Ivan Perisic and Shinji Kagawa.
It also meant Dortmund, who are now eight points clear of Bayern with two games to go, extended their unbeaten league run to 26 games.
Dortmund, for whom it was an eighth Bundesliga crown, can clinch a domestic double when they meet Bayern in the final of the DFB-Pokal on May 12.
Fourth-placed Gladbach remained on 56 points - six points ahead of Stuttgart in the race for the Champions League qualification spot.
A party atmosphere almost intensified when Dortmund came close after 20 minutes. Kagawa's shot came back off the left post and Gladbach keeper Marc-Andre ter Stegen made a superb save to deny Robert Lewandowski from the rebound.
It took just three minutes for the deadlock to be broken, though, Marcel Schmelzer whipping a free-kick into the box and Perisic headed in from six yards.
Gladbach appeared to level after 34 minutes through Mike Hanke but Filip Daems was ruled offside.
Dortmund went close again in the 37th minute as Schmelzer looped the ball over the defence but Mats Hummels could not beat ter Stegen one-on-one.
The visitors almost equalised eight minutes after the break when Marco Reus - who will join Dortmund in the summer - skipped past home keeper Roman Weidenfeller but saw his effort smuggled to safety by Schmelzer.
The crucial second goal came just before the hour mark as a trademark counter-attack down the left culminated in Schmelzer and Lewandowski combining to set up Kagawa, who fired inside the near post.
The hosts nearly finished the game off three minutes later but ter Stegen made a superb save to keep out Lewandowski's header from a free kick.
Gladbach nearly pulled a goal back but Martin Stranzl headed over the bar in the 69th minute.