Tim is the brother of Phil and before becoming his caddie he was agent for fellow golfer Jon Rahm.
He also used to coach golf at Arizona State.
Tim became the full-time caddie for Phil back in December 2017.
The decision was made after he a caddie part time for the five-time major winner and impressed.
At the time Mickelson said: “The last four months or five months have been so much fun and I’ve enjoyed having Tim work with me so much.
“He is a really good caddie.
“He knows my game very well, he knows what I do – what I should do.”
Who was the previous caddie for Phil Mickelson?
Mickelson split from long-term caddie Jim “Bones” Mackay in June 2017.
He had been the man on the bag for the American for an incredible 25 years.
Mackay was the caddie for all five of Mickelson’s majors – the 2004, 2006 and 2010 Masters, 2005 PGA and the 2013 Open Championships.
Speaking about Mackay, Mickelson explained after the split: “I’ve cherished these last 25 years together with Bones.
“We’ve gone through highs and lows on the course. We’ve gone through highs and lows off the course.
“So we have this relationship that spreads (beyond) a lot more than just golf.
“It goes out into a real friendship.”
Mickelson and Woods are playing 18 holes at Shadow Creek in Las Vegas with the winner earning a whopping £7m ($9m).