The gameplay of Final Fantasy III combines elements of the first two Final Fantasy games with new features. The turn-based combat system remains in place from the first two games, but hit points are now shown above the target following attacks or healing actions, rather than captioned as in the previous two games. Auto-targeting for physical attacks after a friendly or enemy unit is killed is also featured for the first time. Unlike subsequent games in the series, magical attacks are not auto-targeted in the same fashion.

The experience point system featured in Final Fantasy makes a return following its absence from Final Fantasy II. The character class system featured in the first game also reappears, with some modifications. Whereas in the original game the player chooses each character’s class alignment at the start of the game and is then locked into that class for the duration of the game, Final Fantasy III introduces the “job system” for which the series would later become famous. Jobs are presented as interchangeable classes: in the Famicom version of the game, all four characters begin as “Onion Knights”, with a variety of additional jobs becoming available as the game progresses. Any playable character has access to every currently available job and can change from job to job at will. Switching jobs consumes “capacity points” which are awarded to the entire party following every battle, much like gil. Different weapons, armor and accessories, and magic spells are utilized by each job. A character’s level of proficiency at a particular job increases the longer the character remains with that job. Higher job levels increase the battle statistics of the character and reduce the cost in capacity points to switch to that job.

Final Fantasy III is the first game in the series to feature special battle commands such as “Steal” or “Jump”, each of which is associated with a particular job (“Steal” is the Thief’s specialty, whilst “Jump” is the Dragoon’s forte). Certain jobs also feature innate, non-battle abilities, such as the Thief’s ability to open passages that would otherwise require a special key item. Final Fantasy III is also the first game in the series to feature summoned creatures, which are called forth with the “Summon” skill.