Poulter claimed the $364,250 winner's purse after holding on at the Phoenix Country Club to beat out Spain's Gonzalo Fdez Castano, who shot a 68 in the final round.
Defending champion Padraig Harrington finished six strokes off the pace after a final round 69.
Harrington beat Tiger Woods with a birdie on the second hole of a playoff last year. Woods, who won the tournament in 2004 and 2005, is not taking part this year.
Luke Donald (71) tied for third with Shingo Katayama, who carded a final round 68.
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