Sri Lanka posted a competitive 271 for 6 after choosing to bat, recovering well from a shaky middle period thanks to Mendis' control and a vital fifth-wicket stand with Janith Liyanage. England's chase began smoothly but unravelled badly once key wickets fell, continuing a worrying run of ODI results for Harry Brook's side.
England made early inroads after a steady start from the Sri Lanka openers. Pathum Nissanka and Kamil Mishara added 50 before Sam Curran broke through, and Adil Rashid then struck twice as Sri Lanka slipped to 124 for 4. Rashid was the pick of the bowlers with 3 for 44, showing his value in the middle overs.
Mendis, however, held the innings together with real authority. He rotated the strike well and punished anything loose, reaching his half-century from 61 balls. Liyanage played the ideal supporting role, scoring 46 as the pair added 88 runs to swing momentum back Sri Lanka's way. Late hitting from Dunith Wellalage, who struck 25 not out from 12 balls, lifted the hosts beyond 270.
England's reply started brightly despite the early loss of Zak Crawley. Ben Duckett and Joe Root put on 117 for the second wicket, with Duckett scoring 62 and Root a composed 61. At 129 for 1, England were well placed.
The game turned rapidly. Both Duckett and Root were trapped lbw, and Sri Lanka's spinners tightened their grip. Brook, Jacob Bethell and Sam Curran fell in quick succession as England slid from control to chaos. Pramod Madushan led the attack with 3 for 39, backed up smartly by Jeffrey Vandersay and Wellalage.
Jamie Overton's explosive 34 from 17 balls briefly reignited hope, dragging England within 20 runs in the final over. But his dismissal ended the resistance, with England bowled out for 252 in 49.2 overs.
Sri Lanka took a deserved 1-0 lead in the series, while England were left searching for answers ahead of the second ODI, also in Colombo.
Sri Lanka Under-19 kept their ICC Men's Under-19 World Cup hopes alive with a composed five-wicket win over South Africa Under-19 in the Super Sixes clash at Bulawayo, sealing victory with 24 balls to spare.
Sri Lanka have named a 16-player squad for a three-match T20 International series against England, using the contest as their final rehearsal ahead of the ICC Men's T20 World Cup 2026.
England's long wait for an away one-day international series victory ended in emphatic fashion as a breathtaking blend of control and power from Joe Root and Harry Brook sealed a 53-run win over Sri Lanka in Colombo and a 2-1 series success.
Joe Root played a match-winning knock to help guide England to a five-wicket victory against Sri Lanka in Colombo and level the three-match ODI series at 1-1.
