The off-label prescribing of antipsychotic drugs to psychiatric patients of all ages is very common. Such off-label use is a necessary part of the art of psychiatry but brings with it increased responsibilities for the prescriber as, if the patient suffered an adverse reaction, liability would rest with the prescriber and/or their employers. This article reviews the frequency and nature of the off-label prescribing of antipsychotic drugs for psychiatric indications to children, adults and the elderly. It also reviews the evidence base for doing so in a variety of common, and also some less common, clinical situations. The review is mainly concerned with off-label indications but a short section on high dose antipsychotics is also included. The review concludes that the off-label prescription of antipsychotics frequently lacks the support of robust clinical trials. When prescribing off-label, the prescriber must carry out a careful risk assessment of the risks and benefits for the individual patient. They should also inform the patient that the prescription is off-label.