- In the parking lot behind the Liberty Tree building in Bedford Point, there is a hidden sign, showing a handwritten message and Rockstar Leeds' signature smiley (as seen on the hidden signs in Grand Theft Auto: Vice City Stories and under the sea north of Bohan in Grand Theft Auto: Chinatown Wars). The PlayStation Portable version says: "Hello again!", while the PlayStation 2 version says "You just can't get enough of this alley, can you?". The sign can be found by jumping over the walls around the lot using a tall vehicle.
- During the storyline, after some major characters are killed by Toni Cipriani, gravestones bearing their names appear in Liberty City Cemetery. Each tombstone (with the exception of Cedric "Wayne" Fotheringay) has a unique message:
References to previous games
- East of Belleville Park, a billboard for the film Let Me Bounce can be seen. The film stars Candy Suxxx, a porn actress from Grand Theft Auto: Vice City.
- Advertisements for the film Sonny Forelli: A True Story can be seen throughout the city. Sonny Forelli was the primary antagonist of GTA Vice City.
- Advertisements for the film The Liberty King can be seen throughout the city. The posters use the promotional artwork of Donald Love from Grand Theft Auto III.
- In Bedford Point, an advertisement for Heat can be seen, which uses a screenshot of Carl Johnson, protagonist of Grand Theft Auto: San Andreas.
- An advertisement for Still Madd, an album by GTA San Andreas character Madd Dogg, can be seen outside the Portland safehouse.
- Around Liberty City (mainly Portland), several graffiti tags of a gang known as "Bully Boys" can be seen. This could be a reference to Bully, another game made by Rockstar Games.
- The Bickle'76, a modified Taxi unlocked via the Taxi Driver side-mission, is likely named after Travis Bickle, protagonist of the film Taxi Driver.
- Throughout Liberty City, advertisements for a film called The Mainframe can be seen. Judging by the name and plot synopsis given in radio commercials, the film is an obvious parody of The Matrix. Interestingly, the characters on the poster are all pedestrians from GTA San Andreas.
- In the mission Rough Justice, Salvatore Leone refers to Toni Cipriani as Lionel when he is dressed in the Lawyer Outfit. This could be a reference to Lionel Hutz, a lawyer in the cartoon series The Simpsons.
- The Dragon Outfit is the same worn by Bruce Lee in Game of Death and by Uma Thurman in wp:Kill Bill.
- Advertisements for the play The Third Leg can be seen throughout the city. "Third leg is slang for a long penis, which the poster depicts.