Background <p>There is substantial symptom overlap in psychosis and autism spectrum disorder (ASD) and co-morbidity is common. In addition, antipsychotic response may be moderated by the co-occurrence. Individuals with ASD may be at greater risk of some clozapine adverse effects and occasionally, its use may be contra-indicated.</p> Case presentation <p>We present the case of a patient with ASD with psychosis unresponsive to multiple antipsychotics, but extra precaution was required with clozapine. </p> Conclusion <p>A multidisciplinary approach is required to establish clozapine in a patient with schizophrenia and ASD</p>