With the widely-anticipated update not due to launch until 23 July, fake streams are already appearing in an attempt to entice players to part with their money.
The new Los Santos resort will offer players the chance to win prizes at casino games like poker, blackjack and roulette, as well as bet on virtual horse and supercar races.
“When the brand-new Diamond Casino & Resort opens its doors, one and all are welcome inside to play, or just to stay in the most luxurious residence in the entire state,” a Playstation blog revealed.
“More than just a place to let go of your inhibitions and your sense of the passage of time, The Diamond is the one-stop destination for quality entertainment, high-end living and a range of experiences you won’t find anywhere else.”
Online GTA players have been awaiting the long-rumoured night spot for months, prompting scammers to seek ways to profit from the excitement.
Videos and live streams are popping up across the internet offering players the chance to win in-game money to use in the casino, though people should be weary of such offers.
Some claim to offer “incredible rewards” for doing “one simple thing” – though that thing is usually no guarantee of receiving money and can actually cost players actual money.
The streamers request that viewers either ‘like’ the video or subscribe to the channel, with some even requesting donations in return for the in-game money.
The decision to add a major casino complex to Grand Theft Auto Online is also likely to attract the attention of regulators, who are concerned about betting in video games.
Other popular forms gambling in games include “loot boxes”, which allow players to pay real money for access to randomly generated in-game items.
Some countries, including the US, have even propose a complete ban on loot boxes over fears they encourage children to gamble.