A developing cartridge includes a first gear, a second gear rotatable with rotation of the first gear, and a first protrusion movable together with the second gear. The first gear includes a first gear portion and a second gear portion having an addendum circle greater than that of the first gear portion. The second gear includes a third gear portion and a fourth gear portion having an addendum circle smaller than that of the third gear portion. During rotation of the second gear from a first rotational position to a second rotational position, the third and fourth gear portions move from a first position where the first and third gear portions engage with each other but the second and fourth gear portions do not to a second position where the second and fourth gear portions engage with each other but the first and third gear portions do not.