Mech Mules often accompany groups of Armacham Technology Corporation soldiers on patrols, as seen in the intro of Intervals 04 and 05. They are bipedal with large rectangular shaped heads and a mounted Gatling gun at the top. They are also armed with mortar launchers, however, only the Mech in Interval 04 uses these.
Due to the smaller size of this Mech, it is questionable whether or not there is a person operating it, as a man would barely be able to fit into it. It may be operated remotely, or it might have its own Artificial Intelligence, much like the Unmanned Aerial Vehicles in F.E.A.R. First Encounter Assault Recon; a product of Armacham's advanced technology. It has weaker armor than any of the REV series and is much weaker than the Enhanced Power Armor. As a result, it is easier to kill than any of the other Mechs encountered in the F.E.A.R. universe. It can also be knocked back by stun blasts from Paxton Fettel. Almost any weapon can disable it, but the Goliath will be the most effective. Despite being the weaker than Power Armor units, Mech Mule is still a formidable enemy, due to the fact that player tends to lack serious firepower when facing them. On higher difficulties, their armament can cause trouble to unprepared players.
- The Mech Mule looks remarkably similar to the Multifunctional Utility/Logistics and Equipment UGCV or, more specifically, the Armed Robotic Vehicle variant, but with legs instead of wheels. These vehicles are also known as the MULE series.
- The Mech Mule in the concept image is armed with a real world LW50MG, while the in-game concept uses the GAU-19.
- Along with the Cannibals, the Mech Mule is not seen in any of the multiplayer maps, thus being a "campaign-only" enemy.