Haas endured a five-bogey, one-birdie round of 74 to finish the tournament at 7-over 287 and claim the $360,000 first prize.
Bernhard Langer, the third-round leader, finished second, a shot back after posting a 76 that he began with a double-bogey after striking a spectator with his opening tee shot.
Scott Hoch, Joey Sindelar and 1987 U.S. Open-winner Scott Simpson finished tied for third, two shots back.
Haas was part of the final threesome'with Langer and local favorite Jeff Sluman'that played the East Course 18 over par on Sunday.
It was Haas 11th victory on the Champions Tour, and came after he won the 2006 Senior PGA at Oak Tree. He also becomes the 13th player to win at least two Senior PGA titles.
Haas clinched the win with a 2-foot par putt on No. 18, coming after he and Langer traded bogeys the previous hole.
Haas 7-over was the highest winning score in relation to par in the 69-year history of Senior PGA, shattering the previous high of 2-over set by Sam Snead in 1970 at PGA National at Palm Beach Gardens, Fla. It also marked the second-highest winning score in Champions Tour history, two short of Arnold Palmers 9-over at the 1981 Senior Open at Oakland Hills.