Whether motor imagery (MI) engages the motor system or relies on perceptual/cognitive processes is a matter of debate. Here we used the size weight illusion to create dissociation between perception and action to address the nature of MI. Participants alternated lifting bricks of equal mass but where one brick was larger than the other, resulting in a perceptual illusion. Fifty-seven participants (M=20, F=37, 22.54.4 years; collected 2019-22) were divided into three groups differing in the modality used for training (MI and overt execution; OE) and exposure to the size weight illusion pre-training (one (MI-2) and five (MI-10 and OE) lifts of each brick). We hypothesized that the MI groups would use lifting dynamics post-training consistent with the illusion, whereas the OE group would maintain accurate lifting forces. Contrary to our hypothesis, the OE and MI-10 groups maintained the effect of the illusion post-training. In the MI-2 group, perception of the bricks’ weight reverted to the participant’s prior belief that large objects are heavy and they correspondingly adjusted their lifting force post-training. These results demonstrate that perceptual and motor processes are engaged during MI, and that the simulation of the motor component of the movement during MI guides the performed action.