The One Direction singer was spotted whiling the night away at the gaming tables at the Pearl Room in Perth and spent most of his time playing chance game roulette.
But Harry's record label bosses have reportedly warned Harry, 19, not to waste too much cash betting after he previously lost an "ugly" amount of money.
An eye witness told the Daily Star newspaper: "One Direction are the biggest band in the world and they certainly earn their time off. But there's having fun on a beach or in a nightclub, and there's high-stakes roulette. It's such an addictive game, and before you know it, you can be up to eyes in debt.
"And although Harry has millions in the bank, it's amazing how quickly it can go. He's his own man and can do whatever he wants, but he's also got his image to protect."
Harry and his bandmates - Zayn Malik, Louis Tomlinson, Niall Horan and Liam Payne - were given their stern warning about the perils of gambling when they blew some of their hard earned cash a couple of years ago to celebrate them all turning 18.
Youngest band member, Harry has the lucky number '17black' tattooed on him to celebrate his love of roulette.
Recalling their birthday bets, Niall said in February: "Like most of the stupid things we do, it seemed like it was a good idea at the time.
'We just thought, 'We're 18, this is the first time we've been able to spend a bit of money in weeks because we've been on the road. I won £100, which seemed reasonable, then I stopped.
"But I'll have to say 'no comment' about the others. Let's just say it got a bit ugly and a lot of money was lost. A lot. When our management found out, we got a serious dressing-down about it."