Having won the toss, the visitors opted to bat first but an impressive bowling performance from Sri Lanka restricted them to 109 runs.
Limmy Thilakarathne, Pramudhi Methsara and Rashmika Sewwandi starred with the ball, claiming 2 wickets each for Sri Lanka.
The hosts managed to cross over the target in the 19th over with 5 wickets in hand. Dahami Senethma and Sumudu Nisansala were the chief architects of the run-chase as they chipped in with useful 20s each.
The second match of the T20 series between the sides will be played tomorrow (6th January) at the same venue.