Opener Jeremy Bray ground out an unbeaten century as Ireland let victory slip after posting a respectable 221-9.
The Irish had appeared in trouble earlier in the day at 89-5, but the Australian-born batsman stayed at the crease for the entire innings to end on 115 not out.
A ninth-wicket stand of 39 off 33 balls with Dave Langford-Smith (15) elevated the minnows’ total and gave them something to defend at Sabina Park.
Meanwhile, Sri Lanka captain Mahela Jayawardene praised his team for a professional approach in their opening World Cup Group B match and said he was looking forward to the challenges India and Bangladesh will provide in the next two games.
Sri Lanka made 321-6from their 50 overs, before swiftly dismissing tournament debutants Bermuda for just 78 with 25.2 overs remaining at Port of Spain.
The 243-run victory was the second highest win margin in the tournament’s history, behind Australia’s 256-run win against Namibia in 2002-03.
Jayawardene said: “The next games will be tougher than Bermuda but this is what makes the World Cup exciting.”
“I think Bermuda bowled well and they will continue to learn. When we played our first tournament in 1975, we were well thrashed by the West Indies.”
