The player is a mercenary in a future where humanity has been driven underground and is ruled by a powerful artificial intelligence called The Controller.

Players operate mech units that they may customize with credits earned from completing missions and fighting in an arena.

Customization extends to every aspect of a player's Armored Core unit, including the individual parts, weapons, paint, and emblem.

In order to earn money to customize their Armored Core, players must complete missions for three major corporations.

[10] Returning after a removal in Another Age, the Arena is a free-form game mode that allows players to fight other pilots to rise in rank.

[9] Winning Arena matches can provide players with credits and parts that can be used on their Armored Core unit.

[11] Like its earlier counterparts, Armored Core 3 hosts a local multiplayer mode that allows players to fight their friends via split screen or console linking with a Sony I-Link Fire Wire cable.

The two major corporations, Mirage and Crest Industries, and a relatively more minor one, Kisaragi, all vie for dominance and control over the land and assets in Layered.

After the player destroys it, an emergency program opens Layered's blast doors and allows for surface access for the first time in centuries.

Eurogamer's Martin Taylor called the variety of objectives "impressive", though later added: "Sadly, the prevalence of missions that have you either bumbling around streets or in various industrial buildings starts to become tiresome and samey" due to "uninspiring locales".

In a mixed review, David Smith from IGN wrote: "From Software could do so much more with these games, and instead it seems committed to doing the same damn thing over and over".