But Sri Lanka’s final total represented something of a recovery after they slumped to 197 for six.
England, however, would have been happy with a target of 287 on a Trent Bridge ground where last year they made 350 for six against New Zealand -- their highest winning total batting second in a one-day international.
Only Mathews and Seekkugge Prasanna, with a quickfire 59, made much headway for Sri Lanka in the first of this five-match series after England captain Eoin Morgan won the toss in this day/night clash.
Pace bowlers Chris Woakes and David Willey both took two for 56 in their maximum 10 overs.
Sri Lanka were 56 for three inside nine overs and their run-rate slowed, with leg-spinner Adil Rashid (none for 36 in 10 overs) proving tough to get away.
It took Mathews 34 balls to score his first boundary -- a reverse-swept four off spinner Moeen Ali.
But a becalmed Dinesh Chandimal (37) holed out off Ali to Woakes at backward square.
Prasanna came to the crease having smashed 95 off just 46 balls, including nine sixes and five fours, during Sri Lanka’s ODI series-clinching win over Ireland on Saturday.
Having been fortunate to edge Ali into the vacant slip area, Prasanna lived up to his big-hitting reputation with four sixes in five balls.
He top-edged a hook off Liam Plunkett over fine leg and then pulled the fast bowler for six over square leg.
Prasanna then twice hoisted Ali high over the legside. And when he pulled a low Plunkett full toss to the midwicket boundary, for his sixth four, it meant Prasanna had completed a 24-ball fifty also including four sixes.
But a miscued pull off the first ball off Woakes’s new spell saw Prasanna caught and bowled, with Sri Lanka then 188 for five in the 34th over.
Prasanna dominated a stand of 68 in 47 balls with Mathews, whose rather more sedate fifty came in 83 balls with a mere three fours.
Mathews eventually holed out off Plunkett before Farveez Maharoof’s 31 not out, at better than a run-a-ball, boosted Sri Lanka’s total.