A developing cartridge comprising: a housing configured to accommodate toner therein, the housing having an outer surface; a developing roller rotatable about a first axis extending in an axial direction; a first helical gear positioned at the outer surface and rotatable about a second axis extending in the axial direction, the first helical gear being rotatable in accordance with rotation of the developing roller; a second helical gear positioned at the outer surface and rotatable in a first rotational direction and a second rotational direction opposite to the first rotational direction, the second helical gear being movable in the axial direction between a first position and a second position positioned farther away from the outer surface than the first position is from the outer surface, the second helical gear being moved to the first position by a first thrust force generated by meshing engagement between the first helical gear and the second helical gear in a case where the second helical gear rotates in the first rotational direction, the second helical gear being moved to the second position by a second thrust force generated by the meshing engagement between the first helical gear and the second helical gear in a case where the second helical gear rotates in the second rotational direction, characterized by the second helical gear being rotatable in the first rotational direction and the second rotational direction about a third axis extending in the axial direction; a cover positioned at the outer surface and covering at least part of the second helical gear; and an engaging member rotatable about the third axis together with the second helical gear and movable in the axial direction together with the second helical gear, the second helical gear being rotatable in the first rotational direction in accordance with the rotation of the first helical gear in a case where the second helical gear is at the first position, the engaging member being engaged with a part of the cover to terminate the rotation of the second helical gear in the second rotational direction in a case where the second helical gear is at the second position a housing configured to accommodate toner therein, the housing having an outer surface; a developing roller rotatable about a first axis extending in an axial direction; a first helical gear positioned at the outer surface and rotatable about a second axis extending in the axial direction, the first helical gear being rotatable in accordance with rotation of the developing roller; a second helical gear positioned at the outer surface and rotatable in a first rotational direction and a second rotational direction opposite to the first rotational direction, the second helical gear being movable in the axial direction between a first position and a second position positioned farther away from the outer surface than the first position is from the outer surface, the second helical gear being moved to the first position by a first thrust force generated by meshing engagement between the first helical gear and the second helical gear in a case where the second helical gear rotates in the first rotational direction, the second helical gear being moved to the second position by a second thrust force generated by the meshing engagement between the first helical gear and the second helical gear in a case where the second helical gear rotates in the second rotational direction, the second helical gear being rotatable in the first rotational direction and the second rotational direction about a third axis extending in the axial direction; a cover positioned at the outer surface and covering at least part of the second helical gear; and an engaging member rotatable about the third axis together with the second helical gear and movable in the axial direction together with the second helical gear, the second helical gear being rotatable in the first rotational direction in accordance with the rotation of the first helical gear in a case where the second helical gear is at the first position, the engaging member being engaged with a part of the cover to terminate the rotation of the second helical gear in the second rotational direction in a case where the second helical gear is at the second position