A developing cartridge (10, 410) comprising: a casing configured to accommodate therein developing agent; a first gear rotatable about a first axis extending in a first direction, the first gear being positioned at an outer surface of the casing, the first gear including: a first gear portion having an addendum circle; and a second gear portion positioned at a position different from a position of the first gear portion in the first direction, the second gear portion having an addendum circle greater than the addendum circle of the first gear portion; a second gear rotatable about a second axis extending in the first direction from a first rotational position to a second rotational position with rotation of the first gear, the second gear being positioned at the outer surface, the second gear including: a third gear portion engageable with the first gear portion and having an addendum circle; and a fourth gear portion engageable with the second gear portion, the fourth gear portion being positioned at a position different from a position of the third gear portion in the first direction, the fourth gear portion having an addendum circle smaller than the addendum circle of the third gear portion; and a first protrusion protruding in the first direction and movable together with the second gear, wherein the third gear portion and the fourth gear portion are movable relative to the casing from a first position to a second position during rotation of the second gear from the first rotational position to the second rotational position, characterized in that the developing cartridge is configured such that, in a case where the third gear portion and the fourth gear portion are positioned at the first position, the first gear portion and the third gear portion engage with each other and the second gear portion and the fourth gear portion do not engage with each other, and in a case where the third gear portion and the fourth gear portion are positioned at the second position, the second gear portion and the fourth gear portion engage with each other and the first gear portion and the third gear portion do not engage with each other. a casing configured to accommodate therein developing agent; a first gear rotatable about a first axis extending in a first direction, the first gear being positioned at an outer surface of the casing, the first gear including: a first gear portion having an addendum circle; and a second gear portion positioned at a position different from a position of the first gear portion in the first direction, the second gear portion having an addendum circle greater than the addendum circle of the first gear portion; a first gear portion having an addendum circle; and a second gear portion positioned at a position different from a position of the first gear portion in the first direction, the second gear portion having an addendum circle greater than the addendum circle of the first gear portion; a second gear rotatable about a second axis extending in the first direction from a first rotational position to a second rotational position with rotation of the first gear, the second gear being positioned at the outer surface, the second gear including: a third gear portion engageable with the first gear portion and having an addendum circle; and a fourth gear portion engageable with the second gear portion, the fourth gear portion being positioned at a position different from a position of the third gear portion in the first direction, the fourth gear portion having an addendum circle smaller than the addendum circle of the third gear portion; and a third gear portion engageable with the first gear portion and having an addendum circle; and a fourth gear portion engageable with the second gear portion, the fourth gear portion being positioned at a position different from a position of the third gear portion in the first direction, the fourth gear portion having an addendum circle smaller than the addendum circle of the third gear portion; and a first protrusion protruding in the first direction and movable together with the second gear, wherein the third gear portion and the fourth gear portion are movable relative to the casing from a first position to a second position during rotation of the second gear from the first rotational position to the second rotational position, characterized in that the developing cartridge is configured such that, in a case where the third gear portion and the fourth gear portion are positioned at the first position, the first gear portion and the third gear portion engage with each other and the second gear portion and the fourth gear portion do not engage with each other, and in a case where the third gear portion and the fourth gear portion are positioned at the second position, the second gear portion and the fourth gear portion engage with each other and the first gear portion and the third gear portion do not engage with each other.