The Deku Mask is one of four Masks used for Transformation,the other three being the Goron Mask, the Zora Mask, and the Fierce Deity's Mask. When worn, it transforms Link into a Deku Scrub. The Mask contains the spirit of the Deku Butler's Son that Link inhabits when donning the Mask, granting him new abilities.With the transformation comes the special abilities of that species; including a new fighting style, the ability to hop across water, a bubble attack that uses Magic Power, and the ability to briefly fly by using a Deku Flower.

Link is first transformed into a Deku Scrub after he follows Skull Kid into Termina, who curses him into this image. The curse is lifted and the Mask is acquired upon learning the "Song of Healing" from the Happy Mask Salesman. In order to achieve this, Link must first retrieve the Ocarina of Timethat was stolen from him by the Skull Kid. The song causes the spirit of the Deku Butler's Son residing in Link to be encased within a Mask, which then falls at his feet. The Happy Mask Salesman then tells Link to keep the mask as a memento.With the mask, Link can freely transform into a Deku Scrub at will.