Call of Duty 3 is a historical first-person shooter game that has a single-player campaign mode and multiplayer mode. It is open-ended, giving the player multiple paths to complete objectives, but plays similarly to the series' previous installment. Players fight alongside AI-controlled teammates against enemies who use various attack patterns, hide behind cover, and regroup to improved defensive positions.
A character can be positioned in one of three stances: standing, crouching, or prone, each affecting the player's rate of movement and accuracy. Two firearms can be carried, and both fragmentation and smoke grenades can also be equipped; unlike previous installments in the series, players have the ability to toss live grenades back at the enemy. Weapons and ammo from fallen foes or friendlies can be picked up to replace weapons in a player's inventory. A player may fire from the hip or aim down the gun's iron sights for increased accuracy. The compass on the heads-up display (HUD) helps the player navigate to the location of each objective.
Using cover helps the player avoid enemy fire or recover health after taking significant damage. Similar to Call of Duty 2, the edges of the screen turn red and the character's heartbeat will increase in volume, indicating that the player's health is low; it can be replenished through an automatic recovery system when the character is not taking fire.