A toner cartridge includes a casing, an auger rotatable about an axis extending in a first direction, an auger gear rotatable with the auger, an agitator aligned with the auger in a second direction, an agitator gear rotatable with the agitator, and a detection gear positioned opposite to the auger gear with respect to the agitator gear in the second direction. The detection gear is rotatable from a first position to a second position. At the first position, a through-hole or a cutout of the detection gear is positioned farther away from the auger than an outer surface of another end portion of the casing in the second direction is. At the second position, a portion of the detection gear different from the through-hole or the cutout is positioned farther away from the auger than the outer surface of the another end portion of the casing is.