Batting first, Ireland recovered from early setbacks to post an imposing 182 for 9. Captain Lorcan Tucker anchored the innings with a composed 50 off 36 balls, while Gareth Delany smashed 49 from 32 deliveries to provide the late flourish.
George Dockrell also chipped in with a quick 19 as Ireland crossed the 180-run mark.
India's bowlers had their moments, with Harshit Rana returning impressive figures of 3 for 24. Arshdeep Singh and Axar Patel claimed two wickets each, but Ireland's middle order ensured the hosts finished with a challenging total.
In reply, India looked on course for a successful chase thanks to Abhishek Sharma's explosive 49 off just 20 balls. However, once the opener fell one run short of his half-century, Ireland wrestled back control.
The hosts triggered a dramatic batting collapse as India's middle order failed to capitalize on the solid start. Shivam Dube scored 25, while Tilak Varma (19) and Axar Patel (15) made useful contributions, but none could convert their starts into a match-winning innings. India were eventually bowled out for 148 in 18.5 overs.
Matt Hollard and Matthew Humphreys starred with the ball, claiming three wickets each, while Jai Moondra picked up two crucial scalps. Gareth Delany also chipped in with a wicket as Ireland completed a memorable all-round performance.
The landmark victory marked Ireland's first-ever T20I win over India and handed the hosts a deserved 1-0 lead in the two-match series, leaving India needing a win in the second match to level the series.
