A unit in Phantasy Star Online 2 is a protective item that grants bonuses to a character's defenses while equipped. As with weapons, players can grind units to improve their bonuses, and can add and modify abilities on units.

A character has three slots to equip units. The first slot accepts a rear unit or sub unit, the second slot accepts an arm unit or sub unit, and the third slot accepts a leg unit or sub unit.

Sub units are not visible to other players when worn. Rear, arm, and leg units can be either shown or hidden at the player's option.