How to Do the Zombie Mod in "GTA: San Andreas"

By Jacob Michael

Updated September 22, 2017

Items you will need

  • CLEO Library (if using Zombie Alarm)

  • IMG Tool (if using BioHazard Alert)

“Grand Theft Auto: San Andreas” or “GTA: SA” is an action-adventure game that combines the thrill of destructive criminal behavior with an open-world environment. The PC version of the game allows for game modifications; users can install new cars, weapons or characters into their game, changing the game-play and action. There are also two mods that add zombies to the game: Zombie Alarm, which must be installed using the CLEO tool, and BioHazard Alert, which is installed manually using IMG Tool.

Zombie Alarm

Download and install the latest CLEO library from the official CLEO website.

Download and unpack the Zombie Alarm CLEO mod.

Copy the “REvil.img” file into the “models” folder, located in the root install directory of "GTA: SA."

Copy the “gta.dat” file into the “data” folder.

Copy the “ped.ifp” file into the “anim” folder.

Copy the “ZombiAlarmStart.cs” and “” files into the “CLEO” folder.

Launch “GTA: SA” and load a game.

Press the “Backspace” key to begin a Zombie Alarm mission.

BioHazard Alert

Download and install the latest version of Biohazard Alert. A folder of modified game files will be installed into the “GTA: SA” directory.

Download and install the latest version of IMG Tool from the official IMG Tool website.

Launch IMG Tool, click “File” and then click “Open…”

Select the “gta3.img” file from the “models” folder of your “GTA: SA” install directory. A list of game files will appear.

Click “Edit” and then select “Add with replacement” from the menu.

Browse to the “gta3 img” folder and click and drag the cursor to select every file in the folder. Click “Okay.”

Click “File” and then click “Rebuild Archive.” The new “gta.img” file will save.

Launch “GTA: SA” and start a new game.


Make backup copies of your original game files if you wish to revert back to vanilla "GTA: SA" in the future.


Installing two or more mods at the same time may result in conflicts or odd in-game behavior.