Cassowaries are rare flightless birds found on the Rook Islands. They are vicious animals that are territorial by nature, and are often seen in groups three to five. Their hide can be used for crafting things and Rook Island natives once traded them as a valuable commodity.

Cassowaries may appear harmless, but they can be one of the more dangerous animals in the game of Far Cry. When aggravated, they move swiftly with the goal of chasing the player out of their territory. They attack by either slashing with their talons or ramming the player with their crest. Both attacks cause relatively significant damage. Their threat is compounded by the fact they usually travel in packs of three to five and they will attack if the player gets too close.

The plus side is that cassowaries are easy to kill. They are not particularly strong and get killed by a single arrow anywhere on its head or body. Using an automatic rifle can quickly eliminate an entire flock of them without difficulty. Due to their territorial nature, they will flee from the area if shot at from far away but will return to attack if the player remains in the area for too long. More significantly, cassowaries are arguably some of the easiest wildlife to identify on Rook Island through their calls, making both tracking and alerting of their presence quite easy. They will also defend themselves if they are chased into a corner.