The story revolves around Jason Malone, a skilled mixed martial arts fighter who is targeted by Frank Veliano after winning in a match.

Much like the Grand Theft Auto series, Gangstar Vegas has elements of driving games and third-person shooters, and features "open-world" gameplay that gives the player more control over their playing experience.

In addition to the main story missions, players can freely roam and/or partake in several side-activities like gang wars, bank robberies, street racing and underground fighting tournaments.

In keeping with the game's Las Vegas theme, casino minigames such as video poker, blackjack and slot machines were also introduced, along with several establishments such as a nightclub and convenience stores.

The player can join "parties" in the gang wars with flamethrowers, Molotov cocktails, grenade launchers, and many more lethal weapons.

Professional MMA fighter Jason "the Kid" Malone is bribed by the casino owner and powerful Mafia boss Don Frank Veliano to take a dive in a match against Pietro Holston.

As a result, he is chased by Frank and his henchmen before Karen Olsen, the accountant and bodyguard of Vera "Leatherface" Montello, arrives and helps him escape.

Jason later works for the Montello queenpin, Karen and Eric (more commonly known as "E-Man"), a pimp and drug maker-dealer, mostly in causing chaos against the Velianos.

They then rescue her and escape Frank's soldiers, but at the cost of Vera sacrificing herself to stop reinforcements out of remorse, having also bribed Pietro to lose the MMA fight that led Jason being chased by the Velianos in the first place.