Knives are all kit weapons featured in Battlefield 3, providing two ways to utilize them, the standard knife slash or the Knife Takedown method. The weapon can also be used in all three modes in the game (singleplayer, co-op, and multiplayer).
Knife attacks (whether quick or standard) can destroy chain link fences and window glass with a single blow, allowing passage through them (although there are some exceptions such as the Russian spawn building windows in Operation Métro).
When attacking with a knife, the player does not appear on the radar; however, knife sound effects may reveal their position.
|Knife||Standard issue combat knife based on the M9 Bayonet, the Knife is capable of quick, clean, silent kills when approaching a target from behind and claiming the victim's Dogtags in the process. Slash attacks from the front can be lethal with multiple attacks, however they will not result in Dogtag trophies.||
|ACB-90||Advanced Combat Blade model 90 is a heavy duty combat blade with a razor sharp edge, partly serrated and complete with a gut hook at its tip. This premium piece of equipment allows for quick, clean, silent kills when approaching a target from behind and claiming the victim's Dogtags in the process. Slash attacks from the front can be lethal with multiple attacks, however they will not result in Dogtag trophies.||
After initiating a takedown against a standing or crouching enemy, if the enemy turns to face the player at the last second, a unique frontal takedown animation will be shown.
|Standing||Front||The attacker grabs the target's weapon and stabs him in the chest. He steals his dogtags as he falls to the ground.|
|Left||The attacker shoves the target's weapon down and stabs him under the chin. He grabs the target's dogtags with the blade hilt as he drops him to the ground.|
|Right||The attacker grabs the target's shoulder and spins him around. He stabs the target in the chest, grabs his dogtags, and shoves him to the ground.|
|Back||The attacker pulls the target back by the shoulder, reaches over and stabs him in the chest. He grabs the target's dogtags with his index finger and pulls the knife out.|
|Crouching||Front||As the target turns to the attacker, the attacker pushes him back by the shoulder and stabs him in the chest. The attacker grabs the target's dogtags as he falls to the ground.|
|Left||The attacker shoves the target's weapon down and stabs him in the chest. He releases the weapon and grabs the target's dogtags before removing the knife.|
|Right||The attacker pushes the target onto the ground and stabs him in the chest. The attacker grabs the target's dogtags as he stands back up.|
|Back||The attacker pulls the target back by the shoulder and quickly stabs him in the chest. The target falls back in shock as the attacker pulls his dogtags off.|
|Prone||Front||The attacker lunges down, reaches over the target's weapon, and stabs him in the throat. The attacker nabs the target's dogtags with the knife blade and stands back up.|
|Left||The attacker reaches down from the left and stabs the target in the throat. The attacker nabs the target's dogtags with the knife blade and stands back up.|
|Right||The attacker kicks the target in the ribs and rolls him over. The attacker lunges down and stabs the target in the chest, grabs his dogtags with his index finger, twists the knife, and stands back up.|
|Back||The attacker grabs the target from behind and pulls him up slightly. He stabs the target in the chest and steals his dogtags with his free hand.|
- The takedown animations during alpha were considerably longer. DICE switched to shorter animations that incorporate the removal of the victim's dog tags, and keep the first-person view steadier so the player is more aware of their immediate surroundings.
- Mortar users are immune to takedown. Attacks—vehicle operators cannot be taken down, and the mortar is considered a vehicle for gameplay purposes. It is possible to provoke the user into exiting the mortar, although there is a slight risk of being struck by an outbound smoke mortar (the regular HEDP mortar round does not inflict damage until it falls).
- There is a glitch that occurs when performing a takedown on a victim looking downsight, where the victim's cutscene is shown in magnification equal to the optics on his gun.
- A complicated glitch allows players to teleport to an arbitrary point above certain maps after performing a takedown, with enough height to safely parachute down.
- The ACB-90 knife given to Battlefield Premium users is based on the United Cutlery M48 Kommando Survivor Knife.
- Battlelog tracks knife swings under "shots fired".
- It is possible to score a headshot with the quick knife attack, but this cannot kill an enemy at full health.
- A glitch introduced after one of the 2012 patches limited the number of consecutive takedowns to one, causing players to not attack for up to five seconds. It has since been patched in the October 11th server update.
- If caught in a takedown from certain angles, it is possible to counter the attempt with a quick knife attack. Certain animations will place the attacker's body in the victim's crosshairs, allowing the victim's knife attack to kill the attacker if already weakened below 50 health. A few of these even hit the attacker's head, permitting a headshot, but this will only kill if the attacker is already damaged to below 67 health, as the damage from a knife headshot is only 67, as described in this video. Takedowns from behind cannot be countered, nor can takedowns on crouching victims.
- It is possible to score a simultaneous double kill with the knife. This may either be a case of latency causing both enemies to be caught in a takedown, or the "shot" from the takedown on one enemy also striking the second enemy.
- Due to latency, it is possible to stab somebody and die during a specific frame, granting the person a suicide with the knife.
- The Machete is featured on the cover art of Battlefield 3: Aftermath, however does not appear in the expansion pack.