On February 19, 2007 a free downloadable pack was made available for the game. The pack includes four new playable male agents, three of whom have unique, upgradable headgear. A free update was released on May 11, 2007 which allows the player to reset gangs, makes it easier to find orbs, improves stunt ring visibility, enhances targeting and camera angles when driving, and provides several other minor fixes. This update also includes a new ground strike attack.

Two packs of downloadable content were released on May 10, 2007."Gettin' Busy" bonus pack, available for 400 Microsoft Points (US$5), introduces new vehicles and weapons, new side missions, and street racing. As of September 6, 2007, the "Gettin' Busy" pack has been purchased from Xbox Live around 200,000 times. The "Free-For-All" pack, which is available free, adds a mode called "Keys to the City" to the main menu. It allows the player to impound any vehicle and store it at the Agency and allows the player to enter a "Keys to the City" mode that allows them to alter the Agent's statistics or create several items, and other effects, but disables progress within the game.

Unfortunately, the May 2007 title update and downloadable content were linked to a glitch which reset a number of players' saved games when they played the game's co-operative mode. The developers apologized for the glitch and offered a temporary workaround, however, saved games already lost to the glitch were not recoverable. On May 16, 2007, a further title update was released, resolving the issue, in addition to fixing issues with access to the Halo 3 beta.

Some of the new weapons and Agency vehicles that are in the DLC packs.