Sarwan, still trying to hit full stride following a four-month injury layoff, struck four fours and three sixes in the top score of 52 from 27 balls, as West Indies, sent in to bat in the rain-affected, third and final match of the series, reached 152 for four from their allocation of 15 overs.
Rampaul then collected three for 26 from his allotment of three overs, as Ireland were restricted to 136 for seven from their 15 overs at Sabina Park.
The result meant that West Indies swept the three-match series against the Irish, after they won the first match by 31 runs last Monday at the same venue, and the second match by 18 runs also at Sabina Park.
Rampaul struck in the second over, when he removed Paul Stirling for four, but Ireland recovered to reach 38 for one in the fifth over.
West Indies captain Darren Sammy then snared Niall O’Brien, and fellow medium-pace bowler Dave Bernard Jr. struck in the following over to remove Ireland captain William Porterfield for 25 to leave the visitors on 45 for three.
Narsingh Deonarine tightened West Indies’ hold, when he collected Kevin O’Brien for 13 in the eighth over to leave Ireland 63 for four. But West Indies nerves were frayed, when Nigel Jones joined Trent Johnston and put on 46 for the fifth wicket.
Sulieman Benn then removed Jones for 21, and Rampaul added the scalp of Johnston for the top score of 39 to reduce Ireland to 114 for six in the 14th over, and sink their hopes.
Earlier, West Indies lost Shivnarine Chanderpaul run out for a duck in the first over, but Andre Fletcher hit six fours in 27 from 17 balls to get West Indies moving.
After he was caught at backward point off Kevin O’Brien in the fifth over, left-hander Wavell Hinds and Sarwan came together, and put the match out of reach of Ireland with a stand of 81 for the second wicket.
Sarwan fell in the 13th over to Alex Cusack trying to increase the tempo, and Hinds two balls later, when Johnston held a stunning one-handed catch at third man off Peter Connell before Sammy came with his late typical flourish to give the innings a late boost.
Both sides are using the matches to fine-tune their preparations for the Twenty20 World Cup, which opens on April 30 in the Caribbean.
West Indies and Ireland are drawn in Group-D of the competition, alongside England.
