The visitors’ chase got off to a disastrous start as Mavi struck the ball early to remove Pathum Nissanka and Dhananjay de Silva.
The 24-year-old Mavi later made a dream debut by partnering the pair of Wanindu Hasaranga and Mahesh Thikshana.
Sri Lankan captain Dasun Shanaka provided some resistance with a 27-ball 45, but his team was unable to build on his knock and fell just short of their target.
Mavi said, “I was waiting for this moment for the last six years. The injury happened in between and I felt that my dream would never come true.”
The second T20 of the series will be played on Wednesday at the Maharashtra Cricket Association Stadium in Pune.