Poulter finished at 22-under-par 266 for a five-shot victory over Ignacio Garrido. He made his first two bogeys of the week in the final round, but also had five birdies.
Garrido fired a 6-under 66 on Sunday, moving up from ninth place overnight into second place at 17-under 271. It was his best finish since he claimed his second European Tour victory at the 2003 Volvo PGA Championship.
Philip Price had a 5-under 67 and ended alone in third place at 16-under 272 for his best finish since claiming the 2003 European Open.
Among the three European Ryder cup teammates in the field -- Padraig Harrington, Jose Maria Olazabal and Darren Clarke -- Harrington had the best tournament.
Off to the K Club for Friday's start, Harrington shot a 3-under 69 and tied for fourth place with Christian L. Nilsson at 15 under.
Olazabal had a great Sunday, firing his second consecutive 67 to tie for eighth place with two others at 13 under.
Competing for the first time since the August death of his wife, Heather, from cancer, Clarke had a 72 on Sunday and tied for 31st place at minus-7.
Poulter, 32, didn't have a bogey until he made a four at the par-3 13th on Sunday -- his 67th hole.
It was quite a week for the player who said the only reason he entered this event was to do well enough to crack the world top 50, which he is guaranteed now.
'I came here to do the job and it's good to come and do it,' said Poulter, who entered the round with a four-shot lead and was never close to giving it up.
'Today was difficult because I had the four-shot lead. I just had to keep hitting fairways and greens and roll a few putts in, which I did, and managed to keep myself well in front. I was cruising really.'
The win represented Poulter's fourth top-10 finish worldwide this season.
'I have played as well as this all year,' he said. 'I haven't done anything different this week apart from roll a few putts in and I have won comfortably. It's all about getting the ball in the hole and I have done that very nicely this week.'
Defending champion Raphael Jacquelin had another strong finish here, closing with a 1-under 71 to tie for sixth place with 2003 champion Ricardo Gonzalez (73) at 14 under.
David Griffiths (69) and Steve Webster (69) joined Olazabal in eighth place.