The Twenty20 world champions piled up 211-6, the highest total of the Aichi-Nagoya Games, thanks to blistering half-centuries from opener Abhishek Sharma (61) and Tilak Varma, who smashed 51 not out off 22 balls.
Hasan Nawaz's defiant 96 kept Pakistan in the hunt, but they finished on 192-6.
Abhishek took charge after India captain Shreyas Iyer chose to bat at the Korogi Sports Park.
Pakistan opened with spin from both ends, but Saad Masood was pulled from the attack after his first over went for 24.
Vaibhav Sooryavanshi, who had hit Masood for two sixes, botched a reverse sweep against Saim Ayub and was caught behind. Ayub sent the 15-year-old off with a rocking-baby celebration.
Sanju Samson soon followed, but Abhishek, ranked second in the world among T20 batters, raced to a 20-ball fifty with a burst of big hitting.
It was far from a chanceless innings though. Abhishek survived a run-out chance, and in one over he twice hit shots that landed agonisingly short of Ayub.
He struck seven sixes and three fours in his 28-ball knock before Arafat Minhas had him stumped in the eighth over, ending the onslaught.
The sixes dried up after that, but India were well placed at 114-3 at the halfway mark.
Minhas then bowled Ishan Kishan, but Varma, who reached his fifty in 21 balls, took India past 200 with a late surge.
Chasing 212, Pakistan needed a fast start but limped to 76-3 at the halfway stage instead.
Jasprit Bumrah kept things tight, and spinner Axar Patel removed Usman Khan and Maaz Sadaqat (23) to leave Pakistan struggling.
Nawaz kept their hopes alive but got little support and fell to the last ball of the match.
Earlier, Sri Lanka beat Bangladesh by 63 runs to take bronze.
India's women won gold after beating Sri Lanka by 147 runs in the final on September 22.