Nuwan Kulasekara top scored, from No 8, with an undefeated 42 from 34 balls, including three fours and the only two sixes of the innings.
He received good support from Ashan Priyanjana who made 31 and Ajantha Mendis who cracked three boundaries in his 18 not out from just nine balls.
With Kulasekara, he put on 43 in the last 22 balls to help Sri Lanka to a total of 219 for eight from their full 50 overs.
And for much of the innings Ireland's bowlers capitalised on the absence of star batsmen such as Mahela Jayawardene and Kumar Sangakkara, the latter currently playing for English county side Durham.
Midlesex paceman Tim Murtagh was the pick of the seven Ireland bowlers with two wickets for just 21 runs from his full 10 overs.
Murtagh took a wicket with the fourth ball, having Kusal Perera brilliantly caught low at second slip by Kevin O'Brien and Ireland maintained the early pressure when Lahiru Thirimanne was caught behind in the ninth over with the total on 25.
Kithruwan Vithanage followed almost immediately, caught at slip in Paul Stirling's first over and at 97 for five in the 30th, there was no doubting which side was on top.
But Sri Lanka captain Angelo Mathews led the fightback and the tail impressively completed what could be a decisive turnaround on a slow pitch which promises to favour the tourists' spinners.
