Chalmers three-putted for bogey from 75 feet on the second extra hole to edge Bjornstad, who pulled his tee shot on the par 3 into the water and missed an 8-foot putt that would have forced another hole.
Chalmers became only the second player in the tours 19-year history to win a playoff with a bogey. All but one of the previous 126 playoffs ended either with an eagle, birdie or par.
This feels really good to win this early in the year, said Chalmers, who joins fellow Aussies Jarrod Lyle, Ewan Porter, Gavin Coles and Aron Price in the winners circle. Ive been playing very nicely to this point. I felt this kind of win was just around the corner for me and its nice to actually turn that corner.
Chalmers and Bjornstad closed with 2-under 70s to finish at 14-under 274 on The Dominion Club course. Neal Lancaster (71) finished third, a shot back when his 40-foot birdie putt on the final hole of regulation stopped inches away from the cup.
Chalmers and Bjornstad returned to the tee at the 537-yard 18th, where they each made par. Chalmers laid up on the par 5 and two-putted for par, while Bjornstad went for the green in two and settled for par when his 12-foot birdie putt missed. That sent the two over to the 191-yard ninth hole, which shares a green with No. 18.
I was really nervous, Bjornstad said. I really played solid today. Its a learning experience. Those were not the best two holes in my life.
The 34-year-old Chalmers earned $90,000 to jump to second on the money list with $161,154. The top 25 at the end of the year will earn 2009 PGA TOUR cards.
Arjun Atwal (68), Roger Tambellini (70), Jeff Klauk (71), Bubba Dickerson (72), Bryan DeCorso (74) and Matt Hansen (74) tied for fourth at 12 under.