This chapter focuses on body dysmorphic disorder in psychosis, emphasizing delusional conviction about appearance as a key psychotic feature. It discusses debates about delusional versus nondelusional variants of BDD and their relationship to schizophrenia, then sets treatment goals for this population. Assessment includes the BDD-modified Yale–Brown Obsessive Compulsive Scale, the Body Dysmorphic Disorder Questionnaire, and the Body Dysmorphic Disorder Symptom Scale. The treatment module combines Exposure and Response Prevention with mirror retraining techniques and provides guidance on integrating these methods into a unified protocol. The chapter highlights how targeting appearance-related delusional beliefs and compulsive checking can reduce distress and improve functioning in psychotic patients with BDD features.