Electing to bowl on what seemed like a flat deck, Ashwin (4-8) managed his best bowling figures in T20 cricket to skittle out the visitors for 82 in 18 overs -- their lowest score in the shortest format.
Chasing a modest target, India cantered home in 13.5 overs to hold on to their top spot in T20s and continue their winning run before the Asia Cup and the World T20.
It was India's night all the way after Ashwin, who was given the new ball by skipper MS Dhoni, struck twice in the very first over to remove the Sri Lankan openers.
Already fielding a depleted side, the visiting batsmen struggled against a disciplined Indian attack, which had the right mix of youth and experience.
The Sri Lankan scorecard painted a sorry picture with just Dasun Shanaka (19) and Tisara Perera (12) managing double figures as the rest of the batting collapsed.
Sri Lanka though had a few moments to enjoy after top-scorer Shanaka smashed a couple of sixes during his 24-ball stay, but the visitors suffered from lack of partnerships.
Part-time spinner Suresh Raina also chipped in with two wickets.
India probably ticked all the boxes after their opening loss in Pune to not only bowl or bat well, but also get their fielding act together in the three-match series.
India's ground fielding was highlighted by Jadeja running out Seekkuge Prasanna with a direct throw.
With most of the pressure off their back, the Indian batsmen did their job to bring up another T20 series' win after their 3-0 triumph in Australia recently.
Opener Shikhar Dhawan, who hit a maiden T20 fifty in the team's last win on Friday, continued his fine run with an unbeaten 46 to help the hosts register their biggest T20 win in terms of balls remaining.
Rohit Sharma was cleaned up by Dushmantha Chameera but that was only a hiccup in India's march towards victory as Dhawan and Ajinkya Rahane put on an unbeaten 55-run stand.
Dhawan remained the top-scorer in the series with 106 runs from three games while Ashwin was named the man of the series for his nine wickets.
It was Dhoni's first T20 bi-lateral series win on home soil as the World Twenty20 hosts hammered home their status as one of the favourites for the title in March.
