The extension will keep Finchem at the head of the pro golfing organization through June 2016. He has led the tour since June 1994.
"We have accomplished a lot, but there remains a great opportunity to continue to grow over the next four years," Finchem said in a statement. "It is an honor to work in such a wonderful sport with the world's best athletes and a terrific management team. I look forward to continuing to work closely with them in the future."
He is the third commissioner since the PGA Tour was spun off from the PGA in 1968, following Joe Dey and Deane Beman.
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