A developer cartridge comprising: a housing configured to accommodate developer therein; a first gear rotatable about a first axis extending in an axial direction, the first gear comprising: a small-diameter gear portion; and a large-diameter gear portion having a diameter larger than a diameter of the small-diameter gear portion; and a second gear rotatable about a second axis extending in the axial direction, the second gear comprising: a first engagement portion extending along a portion of a peripheral surface of the second gear, the first engagement portion being engageable with the small-diameter gear portion; a second engagement portion positioned closer to the housing than the first engagement portion to the housing in the axial direction, the second engagement portion extending along another portion of the peripheral surface of the second gear, the second engagement portion being arranged at a different position from the first engagement portion in a rotation direction of the second gear, and the second engagement portion being engageable with the large-diameter gear portion after the first engagement portion engages the small-diameter gear portion; and a protrusion protruding in the axial direction, the protrusion being rotatable together with the first engagement portion and the second engagement portion, wherein a rotational locus defined by rotation of the second engagement portion is smaller than a rotational locus defined by rotation of the first engagement portion. a housing configured to accommodate developer therein; a first gear rotatable about a first axis extending in an axial direction, the first gear comprising: a small-diameter gear portion; and a large-diameter gear portion having a diameter larger than a diameter of the small-diameter gear portion; and a small-diameter gear portion; and a large-diameter gear portion having a diameter larger than a diameter of the small-diameter gear portion; and a second gear rotatable about a second axis extending in the axial direction, the second gear comprising: a first engagement portion extending along a portion of a peripheral surface of the second gear, the first engagement portion being engageable with the small-diameter gear portion; a second engagement portion positioned closer to the housing than the first engagement portion to the housing in the axial direction, the second engagement portion extending along another portion of the peripheral surface of the second gear, the second engagement portion being arranged at a different position from the first engagement portion in a rotation direction of the second gear, and the second engagement portion being engageable with the large-diameter gear portion after the first engagement portion engages the small-diameter gear portion; and a protrusion protruding in the axial direction, the protrusion being rotatable together with the first engagement portion and the second engagement portion, a first engagement portion extending along a portion of a peripheral surface of the second gear, the first engagement portion being engageable with the small-diameter gear portion; a second engagement portion positioned closer to the housing than the first engagement portion to the housing in the axial direction, the second engagement portion extending along another portion of the peripheral surface of the second gear, the second engagement portion being arranged at a different position from the first engagement portion in a rotation direction of the second gear, and the second engagement portion being engageable with the large-diameter gear portion after the first engagement portion engages the small-diameter gear portion; and a protrusion protruding in the axial direction, the protrusion being rotatable together with the first engagement portion and the second engagement portion, wherein a rotational locus defined by rotation of the second engagement portion is smaller than a rotational locus defined by rotation of the first engagement portion.