A drive transmission device includes a first gear, a cam configured to rotate in interrelation with rotation of the first gear and capable of changing a state of two members between a pressed state and a pressure-released state, a pressing member configured to press the cam, and a second gear configured to transmit drive to the first gear in engagement with the first gear. At least one of the first and second gears includes first teeth provided at positions corresponding to an engaging region in which the first gear is engaged with the second gear when the state of the two members is changed from the pressure-released state to the pressed state and includes second teeth provided at positions corresponding to a region other than the engaging region. Tooth thicknesses of the first teeth are thicker than tooth thicknesses of the second teeth.