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This is a lore summary, presenting intradiegetic or in-universe information about the subject. For game characteristics and similar data, consult the table on the right.
Game-specific articles
Fallout 3Radroach
FO: New VegasRadroach
Fallout 4Glowing radroach
Fallout 76Radroach
FO TacticsSmall cockroach
Large cockroach
Fallout ShelterGlowing radroach
Van BurenGiant cockroach
Gametitle-FO3.pngGametitle-FNV.pngGametitle-FO4.pngGametitle-F76.pngGametitle-FOT.pngGame tile Fallouit Shelter.png
Gametitle-FO3.pngGametitle-FNV.pngGametitle-FO4.pngGametitle-F76.pngGametitle-FOT.pngGame tile Fallouit Shelter.pngGametitle-FB.pngGametitle-VB.png

Great American cockroaches, colloquially called radroaches or giant cockroaches,[1] are giant versions of the pre-War species that have been mutated by atomic radiation.


Found mainly in underground areas and sewers across North America, which can cause them to be a pest in certain Vaults because they can usually be found in fairly large groups. They feed on the dead, but will go after living creatures if isolated. Their numbers are their biggest advantage. Radroaches live mostly in the areas east of California.[2]

These radroaches are commonly found in the dark, damp and irradiated parts of the Wasteland[1] and look similar to normal cockroaches, save for the fact that they have mutated to be size of the domestic cat. They are generally little more than a nuisance to Armageddon survivors and are less than likely to pose a challenge. Radroaches are territorial and rather aggressive, but not very harmful. Anyone can kill them with their bare hands, and will only attack when they feel threatened by passersby. Although they are winged, they are incapable to flight, likely due to the wing appendages failing to adapt to the rapidly changing body mass. Still, it is possible that the wings are used for inter-species communication.[1] It is said that radroach innards are useful in the treatment of radiation poisoning, and are widely used by tribals for this purpose.verification overdue, remove




Great American cockroaches, colloquially called radroaches or simply giant cockroaches, are giant versions of the pre-War species Periplaneta americana that have increased in size due to prolonged exposure to the radioactive fallout of the Great War.[1]

Irradiated radroach

Icon cut content.pngThe following is based on Fallout New Vegas cut content and has not been confirmed by canon sources.
Gameplay article:

The irradiated radroach appears the same as a normal radroach but with the radioactive aura of a feral ghoul reaver and the ability to heal itself with a radiation blast similar to a glowing one.

Giant cockroach

Mini-FOT Logo.pngThe following is based on Fallout Tactics and some details might contradict canon.
Gameplay articles:

In the Midwest, mutant cockroaches are a common sight in the Wasteland. As in the Capital Wasteland, they can be encountered nearly everywhere, from old buildings to plains. However, they are drastically different and more dangerous than those met in the Capital Wasteland. They have a big, protected main body and small legs, and their saliva is incredibly toxic. They are very aggressive and attack every human unlucky enough to encounter them.

The Midwestern giant cockroaches are more varied than their Capital Wasteland cousins. Their size can also vary - they can be as small as their relatives in the Capital Wasteland or as big as an adult human.


Mini-FOT Logo.pngThe following is based on Fallout Tactics and some details might contradict canon.
Gameplay article:

Roachor is a unique giant cockroach encountered by the Warrior of the Brotherhood of Steel. It is an "advanced" version of a large cockroach, which lived in the Peoria facility. It appears Roachor was affected by the high amount of radiation coming from a strange production device which was used in manufacturing fusion batteries. He is even bigger than any large radroach, being the same size as a car, his body glowing with a greenish radioactivity. His poison is even deadlier than that of Midwestern radroaches.


Radroaches appear in Fallout 3, Fallout: New Vegas, Fallout 4, Fallout 76, and Fallout Tactics, and were to appear in Van Buren. They were also mentioned in Fallout Bible 1.

Behind the scenes

We also have giant cockroaches cos we understand that in the event of a nuclear was they will be the most likely to survive and as every one who watches 50s sci-fi knows they will mutate to enormous size (we took the liberty of introducing a venomous spit).

Tony Oakden, [3]
  • Their inclusion in the Fallout series is probably a nod to the common myth that cockroaches could survive a nuclear apocalypse.
  • In real life, roaches are noted for their relatively high resistance to radiation—about five to ten times that of humans. However, there are other insects and arachnids even more resistant to radiation, including fruit flies and scorpions. Their resistance to radiation can be explained through their cell-cycle. A tissue-cell is most vulnerable to radiation when it divides, but the cells of a cockroach only divides once every time it molts.