Thanks to Avishka Fernando's century and a disciplined spell from Lasith Malinga, the West Indies were held to 315-9 while chasing a massive target of 339.
The West Indies struggled to find their rhythm early in the game, as Malinga dismantled their top order by taking the wickets of Shai Hope and Sunil Ambris in short order.
Chris Gayle reached a milestone by surpassing Brian Lara as the top ODI run-getter for the West Indies, but he failed to capitalize on his start and was caught by Jeffrey Vandersay off the bowling of Kasun Rajitha.
The chase looked bleak after Dhananjaya de Silva ran out Shimron Hetmyer, but Nicholas Pooran and Jason Holder steadied the ship with a 61-run partnership for the fifth wicket. Holder played a steady knock of 26, but Pooran remained the primary aggressor, continuing his fight even after Carlos Brathwaite was dismissed for a low score.
Holder would depart for a patient 26 but Pooran was would continue to wage a lone battle, even after Carlos Brathwaite was dismissed cheaply.
Pooran and Fabian Allen then put together a promising 83-run stand, striking the ball with precision and bringing the West Indies back into the contest.
Fabian Allen managed to score a half-century, but a confusing run-out shortly after left him visibly frustrated. This followed a dominant first innings where Avishka Fernando hit his first ODI century to help Sri Lanka post a formidable 338-6.
Earlier, Fernando smashed his first one-day international century as Sri Lanka scored an imposing 338-6 in the first innings.