Carty smashed his first fifty of the tournament to guide the West Indies to victory in Dhaka with three balls to spare, after India were bowled out for just 145 in 45.1 overs.
West Indian pacemen Alzarri Joseph and Ryan John grabbed three wickets each to restrict the highly-fancied Indian batsman, after the West Indies won the toss and elected to bowl.
Keemo Paul provided crucial support for Carty with an unbeaten 40 as the pair shared an unbroken sixth-wicket stand of 69. The pair steered the West Indies home after they were struggling on 77-5 at the Sher-e-Bangla National Stadium.
Left-arm spinner Mayank Dagar had given favourites India hope after taking 3-25 from his 10 overs to leave the West Indians reeling, but Carty and Paul kept their cool to deny him any more breakthroughs.
All-rounder Paul, who had claimed 2-17 during his bowling spell, hit just one four and one six in his 68-ball knock. 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."
India U19s 145 in 45.1 overs (Sarfaraz Khan 51, Rahul Batham 21, Extras 23, Alzami Joseph 3/39, Ryan John 3/38, Keemo Paul 2/17)
West Indies U19s 146-5 in 49.3 overs (Shimron Hetmyer 23, Keacy Carty 51 n.o., Keemo Paul 40 n.o., Mayank Dagar 3/25) - AFP