Combat Arms gameplay is similar to commercial games such as Mission Against Terror, CrossFire, Counter-Strike, Ghost Recon 2 and Call of Duty. The game offers many different modes of play, including One Man Army, Elimination, Capture The Flag, multiplayer co-op (known as Fireteam), Quarantine Regen, Elimination Pro, Search and Destroy, Seize & Secure, Spy Hunt, Bombing Run, and Hired Guns. During the 2009 winter season of the game, a special mode known as Snowball Fight was introduced, but was later removed. Combat Arms uses a player ranking system based on total experience, using common military ranks that players can obtain. Completing objectives, killing other players, and levelling up one's rank gives the player money in the form of Gear Points (GP), which can be used to purchase new equipment. Equipment includes weaponry, weapon attachments, and accessories for one's character. Players can also purchase equipment from the Black Market (previously known as the Nexon Cash Shop) using NX (Nexon Cash) that is bought with real-world money. Primarily, the Black Market equipment is cosmetically different from regular shop items and have no rank or level requirement that many of the free items require. In addition, some items may only be obtained through the Black Market. All items purchased have a time length of anywhere from 1 to 90 days,(some weapons can be purchased for a permanent duration from the black market shop), after which the gear is deleted from the player's inventory; however, players can buy most NX standard items for permanent with NX and can be extended with the Weapon Renewal Kit, and on the rare occasion, Gear Points.
Combat Arms has over 10,000,000 registered players. The game supports community features such as clans and an in-game friends' list. There is one current official gaming league known as the World Online Gaming League that Nexon America sponsors, in addition to an upcoming league known simply as Combat Arms League.