Though a sequel to Final Fantasy Tactics Advance, the direct story links are few. Luso is a young student ready for summer vacation, but forced to stay late and help the librarian Mr. Randell clean up. Luso arrives in the library to find himself alone, but notices a strange-looking book with only half its pages filled. It seems to leave off waiting for a name, so Luso provides his own. All of a sudden he's transported to the other world of Ivalice. From that point on his time is filled with exploring the world, trying to figure out what happened to him, and how he can return.

As in the other Final Fantasy Tactics titles, gameplay is centered around a grid battle between two small parties. Characters take turns one at a time, with order and frequency determined by their speed. In each turn they have the chance to move as well as perform a single action; not necessarily in that order. Battles usually end by defeating the other party, though there are occasionally other goals, such as defeating the leader or examining special spots in a stage in search of an item. As in Tactics Advance most of the battles are optional rather than necessary to complete the story. Battles, as well as other jobs like deliveries, can be accepted at pubs in cities. No longer do you fight other clans directly for control of areas, but annually attempt to earn control of an area through auctions. However, jilted clans may want to have it out with you after.

In Tactics Advance, the Law system was primarily one of punishment. If a character didn't follow the laws (Such as "No magic" or "No ranged weapons") for a given battle, they could end up in jail. In Tactics A2, however, laws are primarily a system of benefit. In each battle you get to pick a stat bonus from a list you earn throughout the game. If you break one of the laws you'll lose the bonus, and fallen characters can't be revived for the remainder of the battle (though they aren't permanently lost). You also won't get extra loot at the conclusion of the battle.

This game retains Tactics Advance's Job and Ability system, where each race (hume, viera, moogle, nu mou, bangaa, seeq, and gria) has access to certain base classes, and abilities are earned by equipping an item and earning Job Points. A difference is that even characters that don't take place in a battle will earn JP. Certain later classes must be earned by having characters learn enough abilities in earlier classes, and/or completing certain quests from the pub.