After Johnson made a par four on the playoff hole -- the 18th hole at Sherwood Country Club in Thousand Oaks -- Woods' putt for par to extend the playoff curled out of the cup and left him with a bogey.
The two players, who were paired together, came to the last hole of regulation play tied at 13 under par.
Woods hit his approach shot into a bunker in front of the green at the par-four 18th hole, seemingly giving the advantage to Johnson.
But Johnson gave the advantage back by hitting his approach into a pond in front of the green.
Then, hitting a pitching wedge from the water hazard's drop zone, Johnson dramatically holed out the shot for a par four. Woods blasted out of the sand trap to make par as well and set up the playoff.
Johnson, who won $1 million with the victory, called his wedge shot "very lucky."
Earlier, when he put the ball in the pond, "It was just a bad swing -- got caught up in the moment," Johnson said.
This was the 15th edition of the tournament, which benefits the Tiger Woods Foundation, and next year the event is moving to Florida. Woods has won the tournament a record five times.