A developing cartridge includes first and second rotary members. The first rotary member is rotatable from a first position to a second position and from the second position to a third position, and includes a first gear part and a first rib. The first rib extends along an addendum circle of the first gear part. The second rotary member includes a second gear part and a second rib protruding outward in a radial direction of the second rotary member. The second rib is in contact the first rib during rotation of the first rotary member from the first position toward the second position. The second rib is separated from the first rib during rotation of the first rotary member from the second position toward the third position.