Mexico Rex is an action-adventure, third-person shooting game in which a T-Rex dinosaur with guns strapped to the sides of its head goes on a rampage. The player directs the dinosaur's movements and actions. They receive the highest points possible across 16 levels when they direct it to destroy everything in its path. They must also attempt to complete tasks, such as direct the T-Rex to eat a certain number of humans and collect up to three chili peppers per level.
The player initially helps the T-Rex escape a containment area cage. To equip the animal's guns, they must direct it to eat a box of ammunition. When the player shoots a human, they must direct the T-Rex to eat the person. Beyond eating humans, the T-Rex can destroy rock walls, wooden crates, various types of vehicles and buildings, and other objects. In every case, the player knows when the T-Rex is finished with its assault because a horizontal, red health bar disappears from the screen.
Even if the player collects all three chili peppers, Mexico Rex forces them to start over if they fail to help the dinosaur eat the required number of people. It's important to note that the feeding scenes are bloody and graphic. Parents should review the game before allowing their children, especially young kids, to play it.