Openers Brandon King and Evin Lewis have scored half-centuries and shared a 107-run stand in 55 balls as West Indies earned a five-wicket win over Sri Lanka in the first of their three Twenty20 internationals.

Sri Lanka scored 7-179 in their 20 overs after West Indies captain Rovman Powell won the toss and chose to field at Rangiri Dambulla Stadium on Sunday.

In reply, West Indies reached their target on 5-180 with five deliveries remaining to take an early lead in the series.

King smashed a six and eleven fours in his 63 off 33 deliveries while Lewis hit four sixes and five fours in his 28-ball 50.

The pair at times maintained a run rate of more than 13 runs per over to lay a superb platform.

After Lewis was out in the 10th over — caught by Chamindu Wickramasinghe off fast bowler Matheesha Pathirana — the hosts took two more wickets for 21 runs to threaten a comeback.

Yet the West Indies middle order maintained the momentum to take their team over the line despite Pathirana taking two wickets for Sri Lanka.

Earlier, captain Charith Asalanka (59) and Kamindu Mendis (51) led Sri Lanka's batting in posting a competitive total.

Asalanka faced 35 deliveries and hit nine fours, and Mendis clouted two sixes and five fours in his 40-ball knock, while fast bowler Romario Shepherd took 2-39 for the West Indies.

The second match will be played at the same venue on Tuesday.