A developing cartridge includes: a casing; a developer container; a developing roller; an unsealing mechanism; a first rotary body; a second rotary body; and a delayed transmission mechanism. The developer container is sealed to accommodate developer. The unsealing mechanism unseals the developer container. The first rotary body is provided at the unsealing mechanism. A drive force from a drive source is transmitted to the first rotary body and the second rotary body. The second rotary body transmits the drive force to the developing roller. The delayed transmission mechanism delays transmission of the drive force to the second rotary body for at least a prescribed time after transmission of the drive force to the first rotary body is initiated. The prescribed time is equivalent to a time that elapses from a moment the unsealing mechanism begins rotating to a moment the unsealing mechanism has unsealed the developer container.