The Englishman carded a closing 72, one over par, to edge out China's Liang Wen-chong by one shot and complete a wire-to-wire victory.
The 33-year-old held his nerve to make par and secure a first win since the Dunlop Phoenix in Japan in 2007 and first on The European Tour since Madrid the previous year.
Australian duo Adam Scott (68) and Scott Hend (69) finished joint third at eight under, with South African Charl Schwartzel (69), Graeme McDowell (74) and Dane Anders Hansen (70) tied for fifth a further shot off the pace.
Poulter said: “Getting off to the start I did, getting out of the blocks pretty quick, surprised me a little as I was mis-hitting some shots and I made it a little interesting on a string of holes yesterday," Poulter said.
"And coming out today I made some mistakes as well on the front nine and back nine to make it too close for comfort.
"But to stand on the last knowing I had to make five, I was pretty happy.
"The birdie on 13 pumped me up. I was getting angry. I had played so well in spells around here this week and it is just so annoying to just let easy holes slip with two bogeys and then lose the lead.
"Graeme was in front and I felt like I had to do something. And I did, I rolled one in from 30 feet and it gave me a boost after a tiring day."
It was a great day for English golf a Ross Fisher won the Volvo World Matchplay title, beating American Anthony Kim in the final.
Ross Fisher won the Volvo World Match Play Championship in Spain at the weekend, beating Anthony Kim in the final.
The 28 year old from Wentworth won the final four and three after playing an amazing 126 holes in four days.
Fisher's success stopped Kim, 24 in June, eclipsing Seve Ballesteros as the event's youngest ever winner.
And it also means, while the tournament has now left Wentworth after being staged there from 1964 until two years ago, the trophy is going straight back.
Fisher, a member at the Surrey club since his boyhood days, is up to a career-best 17th in the World Rankings as a result.
Earning a cheque for €750,000 also takes last year's European Open champion to fourth on this season's Race to Dubai and he could go top by winning the HSBC Champions in Shanghai next Sunday.
"I'm absolutely ecstatic," he said. "It's been a long, gruelling week, but obviously very worthwhile.
"This course was very physically demanding and I don't think I am the fittest of blokes out here. I know I need to work a lot more in the gym.
"The only thing that's been missing this year was a win. I feel I've been very consistent and to be the leading guy in the Majors (in terms of shots taken) shows my golf has been very good."