- "That's all there is to it. You want your targets to go down? You gotta aim down your sights."
- — Sgt. Foley in "S.S.D.D.".
Iron Sights are a system of shaped alignment markers used to assist the user in aiming and are included on all portable guns in the Call of Duty series except for the Flammenwerfer 35 in Call of Duty: United Offensive, the M2 Flamethrower in Call of Duty: World at War, the Ranger in Call of Duty: Modern Warfare 2, and the Death Machine, Thundergun and Ballistic Knife in Call of Duty: Black Ops. Iron sights exclude the use of optics such as Red Dot sights, ACOG scopes, sniper scopes and the like.
Iron sights are present on nearly all in-game weapons, and are vital for killing an enemy at long range, as "hipfiring" is inaccurate at most ranges greater than about ten to twenty-five yards. Conversely, at very close range, aiming down the sights can be impractical, as in the time it takes to bring up the sights (typically .15 to .50 seconds, depending on the weapon), hip-firing could have already taken out the enemy and denied them the ability to fire back.
While aiming down the sights (ADS), a player's shots become much more accurate than hipfiring. However, while in ADS, the player's walking and turning speed is slowed, meaning moving in ADS is much slower than moving while not aiming. However, Handguns, SMGs, and Shotguns do not restrict walking speed while in ADS. Also, while walking in ADS, a player's footsteps become quieter, as if a player were crouching, or using Dead Silence/Ninja.
Call of Duty 4: Modern Warfare
In Call of Duty 4: Modern Warfare, there are two substitutes for iron sights: the ACOG Scope and the Red Dot Sight, which are unlocked by killing a certain number of enemies. 25 kills on assault rifles, LMGs, SMGs and shotguns earns a red dot sight, and 150 kills on assault rifles, LMGs and SMGs, or 100 kills on sniper rifles, unlocks the ACOG Scope. The singleplayer campaign also features weapons with Holographic Sights, which are similar to Red Dot Sights.
Call of Duty: World at War
In Call of Duty: World at War, there are three substitutes for iron sights: the Telescopic Sight, the Sniper Scope and the Aperture Sight. All three are unlocked after having completed challenges that require kill counts. It takes 75 kills for Rifles and SMGs to earn the Aperture Sight. The Telescopic Sight is only available for the Gewehr 43, SVT-40, FG42 and STG-44. It is earned by achieving 75 kills with the FG42 and 100 kills with the SVT-40, Gewehr 43 and STG-44.
Call of Duty: Modern Warfare 2
In Call of Duty: Modern Warfare 2, there are four substitutes for iron sights: the Red Dot Sight (MARS Sight on the TAR-21 and Integrated RDS on the F2000), the Holographic Sight, the ACOG Scope (The SUSAT on the L86 LSW), and the Thermal Scope. The Red Dot Sight is unlocked after getting a certain amount of kills for the gun, 25 for most, but for others, 10. The ACOG scope is unlocked after 150 kills with the weapon, the Holographic sight is obtained after 60 kills while looking down the Red Dot Sight of that weapon, and the Thermal Scope is unlocked after 20 kills while aiming down the ACOG scope.
Call of Duty: Black Ops
In Call of Duty: Black Ops, there are five substitutes for iron sights; the Red Dot Sight, the Reflex Sight, the ACOG Scope, the Infrared scope and the Variable Zoom. However, there are many different variations to the Red Dot Sight and the Reflex Sight in Black Ops, as the reticle, color of the reticle, and the color of the lens can be altered. On certain handguns, the iron sights can also be upgraded.
Call of Duty: Modern Warfare 3
In Call of Duty: Modern Warfare 3, there are 7 substitutes for the iron sights. They are the Red Dot Sight, the Holographic Sight, the ACOG, the HAMR Scope, Hybrid Sight, the Variable Scope, and the Thermal Scope. The sight can be customized, like Black Ops, but the colors cannot be changed.
- All the weapons in Call of Duty 2: Big Red One have misaligned iron sights.
- Certain weapons in Call of Duty: Modern Warfare 2 have "IW" written at the bottom of the rear sight. This is a reference to Infinity Ward, the developer of Call of Duty: Modern Warfare 2.
- In Call of Duty: Black Ops, the iron sights on several weapons (like the Enfield, Famas, AUG and G11) have "III ARC Firearms" written at the bottom of the rear sight. This is a reference to Treyarch, the developer of Call of Duty: Black Ops.
- Call of Duty: Black Ops is the only game in the series that allows upgrading the existing iron sights on weapons, which makes the iron sights brighter and more decipherable, though this is only available for the M1911, Makarov, and CZ75 pistols.