Sunil Ambris's maiden ODI hundred helped the West Indies complete their highest successful ODI run chase with five wickets in hand in the fourth match of tri-series in Dublin.
Ambris (148) hit 19 fours and a six in his 126-ball innings as the West Indies surpassed Ireland's total of 327 for five with 13 balls to spare.
The West Indies were behind the run-rate at 112 for two in the 20th over.
But a third-wicket stand of 128 between Ambris and Roston Chase (46) helped get their team on track.
Jonathan Carter (43*) and captain Jason Holder (36) saw the West Indies over the line in their second triangular series win.
Earlier, Andrew Balbirnie (135 off 124) scored a brilliant hundred, fourth of his ODI career, of his own in an Ireland total of 327 for five. Balbirnie also passed 3,000 runs for Ireland in the process.
He was supported by Paul Stirling (77) and Kevin O'Brien (63 off 40).
West Indies' victory moved them above Bangladesh and left Ireland without a win after three matches.