One of golf's dynamic duos is no more - Phil Mickelson has parted ways with caddie Jim 'Bones' Mackay.

Mickelson announced on Tuesday that he and Mackay have "mutually decided" to end their professional relationship after more than two decades of working together.

Mackay is the only caddie Mickelson has had in his 25 years as a professional and the pair have combined for 41 PGA Tour victories, including five majors wins.

"After 25 very rewarding and memorable years, Bones and I have mutually decided to end our player-caddie relationship," Mickelson said in a statement.

"Our decision is not based on a single incident. We just feel it's the right time for a change.

"Bones is one of the most knowledgeable and dedicated caddies in the world. He is always prepared and has the ability to make decisions in pressure-packed situations.

"Bones is without a doubt one of the most thoughtful people that I have ever known. The next player to work with him will obviously be very lucky.

"My relationship and history with Bones far exceeds golf. He has been one of the most important and special people in my life since the day we met, and I will always be grateful for everything he has done for me."

Mickelson's brother, Tim, will serve as his caddie for the rest of the season.

Mackay said in a separate statement: "Player-caddie relationships don’t often last that long. I will always be grateful that I was around to witness so much of Phil’s career."