In this article I offer a defence of the use of deceptive placebos—inert treatments like sugar pills or saline injections—in clinical practice. In particular, I will defend what I call the ideal placebo case—where a doctor or nurse has good reason to believe that a deceptive placebo offers a patient’s best, or only, chance of some therapeutic benefit. Taking a Kantian approach to the question of clinical placebo use, I examine the Kantian prohibition on deception as interference with the will of a rational agent, and argue that deception to promote the placebo effect can be carried out in a way that does not interfere with the patient’s will in the way prohibited by Kant. The deception involved in a placebo treatment is not carried out to interfere with or obstruct the function of the will, but merely to make possible a means to the patient’s ends that that would otherwise be unavailable. I will therefore argue that deception carried out in order to promote a therapeutic placebo effect can be done in a way that is consistent with respect for a patient’s autonomy, and may be a rare case of deception that is compatible with a Kantian ethical approach.