The Flamethrower lets out an invisible projectile traveling along the flame stream that causes 50 points of damage. Each projectile eats up 4% of fuel in the 100% tank, meaning 25 "shots" total. The flame projectiles reach out to about 12.5 meters before fading out, almost the range of shotguns. It carries one spare fuel tank, and if reloaded, it substitutes the whole tank, discarding any leftover ammo, unlike all other weapons. The Flamethrower can also be reload canceled. As with the other under-barrel attachments, the flamethrower's ammunition cannot be replenished via Scavenger. If the player is using Warlord, they can't equip any other attachment if the Flamethrower is equipped.
This is a good attachment if the player has a long-range weapon or has run out of ammo and is in a CQC situation. The Flamethrower's flames travel significantly slower than bullets, so it is possible to still kill an enemy after a recent death. However, this also means that the player has to lead a target at a further range. If the player tries to aim directly at a moving enemy, chances are the stream of flame will land behind them. For this reason, it is preferable to have a high sensitivity when using the flamethrower, as this allows sweeping the flamethrower, making it hard to dodge.
In comparison to the Masterkey shotgun attachment, the Flamethrower is outclassed in terms of power, as the Masterkey is capable of one shot kills to an enemy of full health, while the Flamethrower would kill in two shots. However, if one misses a shot with the Masterkey, or should it not kill in one shot, the pump-action will most likely prevent a user from getting the kill, or prove fatal in a close quarter battle, whereas the Flamethrower's stream of flames will likely allow the user to get the kill in those circumstances. Against enemies with Flak Jacket Pro, the Flamethrower is near useless, where as the Masterkey will kill enemies with Flak Jacket Pro. Unlike the Masterkey, however, the Flamethrower will serve as a distraction to targets, as when fired in the face the target will not be able to see anything else.
- In campaign the pilot light doesn't turn on at all, but in multiplayer, once turned on, it stays on even when not being used.
- The pilot light activates when the Flamethrower is readied.
- If the player reloads the Flamethrower before the canister is empty, they will lose whatever fuel was left in the canister.
- If the player drops the weapon with the attachment, and then they pick it back up, the magazine will be full.
- The Flamethrower attachment will give most of the assault rifles a heat shield. The M16, Famas, AUG, and Commando get a full heat shield. The AUG's heat shield is unique in that it is a different type and not spray painted red, like the Red camo. The Enfield, M14, Galil and AK-47 get a partial heat shield. The FN FAL is the only assault rifle not to get a heat shield when it is equipped with the Flamethrower attachment.
- In the campaign, the Flamethrower attachment is only found on AK-47s.
- The Flamethrower is the only underbarrel attachment that does not appear in Nazi Zombies on Pack-A-Punched weapons (except on the AK-47 obtained via modding).
- The Flamethrower attachment uses the same reticle as the Wunderwaffe DG-2 and the Thundergun, albeit a bit wider.
- The Create-a-Class image shows the Flamethrower attached to an M16 heat shield.
- On the mission SOG, if an AK47 with the Flamethrower attachment is picked up when the US Marines are climbing the hill after the napalm barrels part, it will have 100 ammo with nine spares. If this is reloaded before it is finished, the spares will stay at nine and the ammo will refill. This effectively means that it is impossible to run out of ammo for it.
- In singleplayer, this attachment appears to cause no friendly fire, similar to the Thundergun.
- A player's character will scream loudly when hit with the flamethrower in both campaign and multiplayer.
- If the player has this attachment, the pilot light's distortion effect may still be present during killcams.
- In Payback, if the player kills 10 enemies with the flamethrower they get the Russian Bar-B-Q achievement.
- Aiming the Flamethrower at a friendly dog will turn the player's reticle blue.
- The flamethrower is absent from the Wii version of the game.
- When a Weapon with the Flamethrower is picked up, the Flamethrower will always have maximum ammo.