Paceman Joseph grabbed three wickets in his opening spell and finished with 3-39, leading the attack for the West Indies.
After Joseph's 3/39 top order, Ryan John then grabbed three wickets restricting the highly-fancied Indian batsmen.
The same batsmen, who helped India stay unbeaten earlier in the competition, failed to apply themselves in the big game after they were put in to bat by the West Indies and were sent packing for 145 runs in 45.1 overs.
Keacy Carty struck an unbeaten 52 early on, with Keemo Paul providing crucial support with an unbeaten 40, allowing the pair to share an unbroken sixth-wicket stand of 69.
Chemar Holder kept things tight to maintain pressure on the Indian batsmen, conceding only 20 runs in 10 overs with a timely wicket of Mahipal Lomror.
India, aiming for an unprecedented fourth title, lost their top three for 27 runs, all falling to Joseph.
West Indies captain Shimron Hetmyer praised his bowlers in particular for toppling the favourites.
"We weren't supposed to be champions but we came out on top. The pacers used the pitch to their advantage, they stood out for us. Carty and Paul are aggressive players, they made the adjustment. They kept a calm head," he said.
The Caribbeans' performance is likely to embolden critics like former fast bowler Ian Bishop, who have appealed for more programmes to develop young talent.