The tournament was a 36-hole event instead of the usual 72 holes because of rains that made the Riviera Country Club course virtually unplayable.
Scott had tied Campbell for the lead at 9-under-par 133 Sunday with a birdie on the last hole of the second round. He won the playoff with a 3-foot par putt after Campbell had missed from about 4 feet.
No other PGA event had been cut to 36 holes since the Buick Challenge in 1996.
"It's been a tough week, very unusual week, but I knew I had to make that putt on Sunday and it worked out in the end," Scott said. "A win's a win."