Fleetwood won USD154,500 (£120,000) for finishing in a tie for 12th at Carnoustie, but that amount was transferred to an American man by the name of Thomas Fleetwood instead.
However, the world number 11 was left waiting for the sum to be deposited to his account after the European Tour, which handles payments for the event, mistakenly sent it to a United States club pro golfer of the same name.
It is believed the European Tour, who along with the PGA Tour are in charge of sending out prize money to the players, already had the former pro's bank account details because he had competed in Challenger Events in Europe decades ago.
A spokesperson for the European Tour said: "This was a clerical error which we are resolving and we apologise for the inconvenience caused to both parties".
United Kingdom golfer Fleetwood has won a cool $9 million in prize money in the past two years - meaning he may have been forgiven for not noticing the oversight immediately.
The problem: It went to the wrong Tommy Fleetwood. "I emailed them back and I said, 'Well, I plan on sending it back, but you've got to excuse me that I'm not going to send it to this thing you're sending me randomly in email. The money's been repaid now - but at least he can say he won $154,480 at The Open".
TOMMY FLEETWOOD feels he is closing in on a first major title ahead of the US PGA Championship at Bellerive, which begins today. It's a amusing story.
Looks pretty legit to me.
Open Tommy Fleetwood, meanwhile, wasn't sweating the mistake.