In 1984, Diego and his brother, Armando, are the two most powerful drug kingpins in Vice City, and are also well known for their philanthropist views. The brothers, who are of Bolivian descent, also control their own crime organisation.
Diego was voiced by Ruben Trujillo.
In GTA Vice City Stories, Diego and Armando are first mentioned by Jerry Martinez in Brawn of the Dead, when he informs Victor Vance that the cocaine shipment that he and his brother Lance had stolen from Martinez actually belonged to the Mendez Brothers.
Because of this, Lance and Victor are summoned by the Mendez brothers to explain the disappearance of their cocaine. The Vance brothers pin the theft on Martinez, and provide fake evidence to prove this. Victor and Lance continue to work for the brothers, including taking over a local biker empire site, rescuing Diego from pursuing bikers, and killing rival drug dealers. Eventually, the Vance brothers outlive their usefulness to Armando and Diego, who order the Vance brothers to surrender their businesses to the Mendezs and leave the city in exchange for their own safety. Victor refuses to do so, so the Mendez brothers attack the Vance brothers and leave them at a fuel depot in Viceport. A Mendez hitman accidentally starts a fire at the depot, but the Vance brothers manage to escape.
With their ties severed, some Mendez Cartel members unsuccessfully try to take over Victor's businesses. Victor, with the help of Ricardo Diaz, hacks a Domestobot owned by the brothers and uses it to destroy the contents of their safe. In retaliation, the Mendez Cartel kidnap Victor's girlfriend Louise. Louise later dies, and Victor murders Armando in retaliation. Following Armando's death, Diego goes into hiding in the Cartel's downtown offices. Victor steals a military helicopter and uses it to attack the Mendez Building. After being shot down, Victor enters the building and fights his way to the roof, where he confronts both Diego and Jerry Martinez. Victor kills both Diego and Jerry, wiping out the Mendez's presence in the city.
In contrast to Armando's charismatic and open personality, Diego is quieter and more reserved, and only communicates in Spanish. Despite being active within the cartel's operations, Diego tends to leave the business matters to Armando. When he is not working, he can often be seen reading alone, and, as shown when Victor tries to converse with him, can become annoyed if he is interrupted. It is also implied that Diego once had a relationship with Reni Wassulmaier. According to Armando, both he and Diego are utilitarians, with Diego being a fan of Plato's work and Armando being a fan of Aristotle's work. Utilitarism is the theory that mankind should always look towards finding pleasure, which is highlighted by both brothers becoming drug dealers for personal gain.
The Mendez Brothers are possibly based on the character's of the 'Diaz Brothers' a pair of fraternal drug dealers who are mentioned in the 1983 film Scarface. Their names are a reference to Argentinean footballer Diego Armando Maradona.
- GTA Vice City Stories
- Blitzkrieg (Post mission pager message)
- The Mugshot Longshot (Boss)
- Taking the Fall (Post mission pager message)
- Unfriendly Competition (Boss)
- Farewell to Arms (Post-mission pager message)
- Burning Bridges (Boss/Betrayal)
- Last Stand (Killed)
- In Diego's artwork, he is holding a Beretta M12 sub-machine gun, which is absent from the game.
- Like Massimo Torini from GTA LCS, Diego does not directly talk to the protagonist. Although unlike Toni, Victor actually tried to converse with him in the mission Unfriendly Competition while he was reading a book, although Diego gets frustrated and tells his brother in Spanish to meet with Vic.
- Armando Mendez - Diego's brother.
- T-Bone Mendez - A character in Grand Theft Auto: San Andreas with the same surname.