Driver Gerardo Gamboa found the cash in a bag in the backseat of his cab Monday and realized it was from a passenger he drove brought to Palms Place from the Cosmopolitan, the Las Vegas Sun reported.
Gamboa told his employer, Yellow Checker Star, which tracked down the gambler, verified his identity and returned the cash.
The gambler, whose name was not reported, requested to meet with Gamboa to thank him and get his contact information to give him a reward, which turned out to be $10,000.
It was previously reported that Gamboa received a $1,000 reward and dinner at an exclusive Las Vegas restaurant.
Gamboa, a 13-year driver for Yellow Checker Star, was later named the company's Driver of the Year for his honesty.
"He's absolutely awesome; he's one of our stars," company Field Operations Manager Joel Willden said of Gamboa.
Gamboa said he wasn't sure what he would do with the extra money.
"I'm taking it to the bank for now. But after that, I don't know what is going to happen," he said.