Pathum Nissanka sent Sri Lanka's chase screaming out of the blocks, before Kusal Mendis and Kusal Perera put on a clinical and unbeaten 106-run stand for the second wicket.
For a team that had never before beaten West Indies in a T20I series, this chase was almost too effortless to believe. Each of the top three produced sparkling innings, as the hosts galloped to the target of 163 with 12 balls remaining, in front of a packed Poya-day crowd in Dambulla.
West Indies had earlier done well to get to 162 themselves, though they largely have a late assault from Gudakesh Motie - who bludgeoned 32 off 15 - for getting to what was perhaps a higher-than-par score on a spin-friendly track.
Though Dunith Wellalage went for runs, Sri Lanka's remaining spinners kept a lid on the scoring. This too, was a key difference between the teams.
Kusal Mendis went on to register the game's highest score, with 68 not out off 50. Perera crashed 55 off 36. Nissanka had played the most aggressive innings, plundering 39 off 22.
The 2-1 result is a further sign of resurgence from Sri Lanka, in the format in which they have arguably struggled the most in the last two years. They have this year won five Test matches, and had in July beaten India in a bilateral ODI series as well. This win also sees new coach Sanath Jayasuriya's stock rise further.
Sri Lanka attack early
West Indies bolstered their spin attack by bringing Fabian Allen into the side for this match, but Nissanka ensured Sri Lanka's batters established their dominance early.
He cracked three fours off the first over, bowled by Allen, before launching seamer Alzrri Joseph for two sixes and a four next over - the runs coming all around the ground, though he did favour the square region on the offside. By the time Nissanka was bowled by a Motie slider after 5.2 overs, Sri Lanka had already sped to 60.
Kusal Mendis and Perera consolidate, then accelerate
The early middle overs were quieter than what had come before. But soon, Perera began to find the boundary particularly off his legs, and the Sri Lanka run rate was off again, before West Indies could apply serious pressure.
Kusal Mendis, who had begun to score rapidly towards the end of the powerplay, continued to strike regular boundaries as he strode to a 15th T20I fifty. Perera reached his half century - also his 15th - in what became the final over of the game.
West Indies miss chances
West Indies had chances to dent the chase. Rovman Powell could have caught the dangerous Nissanka in the first over, but misjudged the high ball and palmed it into the rope instead. Later, Roston Chase dropped a straightforward return chance off Kusal Mendis on 44 - though Sri Lanka were well en route to victory by then. Shai Hope could have run out Kusal Mendis on 34 too, had he hit the stumps with a throw in the ninth over.
Motie's mauling
The high-point of West Indies' innings, was the 15th over of the match, in which they reaped 25 runs. Their innings had been flagging at 86 for 5 after 14 overs, with plenty of spin to come from Sri Lanka. But Motie would lay into left-arm spinner Wellalage to revive the innings. His first boundary came off the outside edge, but the next three were towering, successive sixes - the first down the ground, the next two over deep midwicket. He was out soon after, but set West Indies on a better course.
Scores:
Sri Lanka 166 for 1 (Kusal Mendis 68*, Kusal Perera 55*) beat West Indies 162 for 8 (Powell 37, Motie 32, Theekshana 2-19) by nine wickets
