Zombies are caused by capsules, with black figure and white eyes; they have brought about the end of civilization and remain a constant threat to anyone exploring derelict stations. They come in several flavors:
- basic zombies are barely a threat by themselves, however they usually appear in greater numbers than their tougher variants. It takes four empty-handed punches, one fully charged punch, or three melee hits with the shotgun, two bullets to the body, or one bullet to the head to kill.
- Smaller zombies or tacklers have the ability to run and bite, they can easily overwhelm the player. They are about half the height of a regular zombie.
- Armored zombies wear grey bulletproof armor that protects their body and a visored helmet that protects their head. However, their legs are still vulnerable to attack. a singular punch is needed to knock off their helmet and a headshot is needed to kill. They are mostly found in factories, military facilities, and other important locations.
- Explosive zombies will, as the name implies, explode upon death or contact with the player, dealing huge area damage. If shot but not killed their heads will light on fire and they will explode after a short time.
- Titans or tall zombies are a much stronger variant of the basic zombies, and need more shots or punches to kill them, they will appear to be a threat due to their high health and take 2 fully charged punches to eliminate them.
- 2 New variants of Titans are introduced in the Only Traitor DLC: Crawlers and Frenzies
- Crawlers are a titan variant that can be crippled with 2 - 3 bullets, but they will then proceed to crawl their way to the players feet and swipe after they go down, making it difficult for the players to aim their weapon at them.
- Frenzies are a titan variant similar to a combination of the original and tacklers, shooting at them will cause them to frenzy and make their eyes glow, causing them to run towards the player doing a massive amount of damage, killing the player in 1 - 2 hits. It takes 5 - 6 shots to kill them.
- Jumpers will pounce on top of the player and grab on to their face, preventing weapon firing. They appear quite similar to the smaller zombies. although they have longer arms that reach the floor, short legs, and what appears to be long hair coming from its head, leading many to believe these were female or possibly even children.
- Note that all zombies can be killed with an explosion from an explosive zombie or barrel, or from a hit from a thrown object.
- Acid Zombies can pose a threat to players because they can spew globs of Acid towards the players direction from far to medium distance, they will also hit the player in close combat. It takes 3 - 6 shots to kill them. They have similar features to that of the others but with a green glow in the eyes and mouth.