In Ace Online, players pilot their own individual starfighters (called "Gears") throughout a number of maps, including terrestrial, lunar, and space maps. It has typical MMORPG elements such as leveling, currency, and a skills system. Ace Online is a largely Player vs. Player (PvP)-oriented game, with character leveling and item acquisition achieved through combat against Non-Player Characters (NPCs) and the completion of missions. After completion of certain missions, more maps will be accessible to the player. Although a high level character will have better character attributes than most other players, no one at any level is invincible against other players in PvP. As in other MMORPGs, players can trade items, customize their gears, form parties ("formations") and guilds ("brigades"), and fight with other players via PvP combat. Almost all of the combat in Ace Online is aerial, from the third-person view. Players have the option to use the in-cockpit, first-person view by pressing on the "Delete" key once. This View is rarely used as it restricts vision of the pilot, by cutting down on his/hers peripheral vision as well as increasing difficulty in manuevering the gear.

When players create their account, they can choose from one of four different gears, each with very different play styles. A gear`s performance can be improved with purchases from the "Skill Shop". Skills range from healing skills, weapon enhancing skills and gear performance skills. The magnitude and the duration that the skill effects the gear depends on the level of the gear performing the skill.

New armor is also available at the "Gear Shop", but the armor can only be used if the requirements for that armor are met. The gear cannot take off if no armor is equipped. Armour can be enhanced using various recipes of materials gathered from monster drops which increases the "energy points" and "shield points". Certain enhancements have an additional boost to the "defense" or "evasion" percentage score of your gear. Gears may use "Standard" or "Advance" weapons. The former are basic guns that use the crosshair for targeting, the latter are missiles which can lock-on to gears. Missiles are guided projectiles that require a lock-on to the target, but a Gear may avoid them by barrel-rolling. A specific type of gear can utilize a skill to cause his missiles to do splash damage, among other bonuses

Ace Online is a free-to-play MMO, with the option of buying in-game items via an "Item shop" that can be only accessed whilst in the "City" or "Supply Shop" from bottom right corner of the screen or the shop. In the International Ace Online version, you can only purchase the items from the "Item shop" using yecoins that has been bought through Yedang website via your Ace Online account. There are many items available to purchase that affect your gear`s weapons (e.g change the trail effect of the missiles), stats (e.g resets or partial resets of stats), experience (e.g increase experience rate) or others for a limited time. This item shop was made available to players on June 23, 2006.

Ace Online offers a PvP system of "Nation Wars", which revolves around a point system: "National Contribution Points" (NCP). The two nations in question are Bygeniou City United (BCU) and Anti National Influence United (ANI). Every time an enemy gear is shot down, the shooter`s nation gains 1 NCP. NCP are also gained for other events.