Paranoid personality disorder (PPD) is a severe condition, lacking specialized and empirically supported treatment. To provide the clinician with insights into how to treat this condition, we present a case study of a 61‐year‐old man with severe PPD who presented with ideas of persecution, emotionally charged hostility, and comorbid antisocial personality disorder. The client was treated with 6 months of Metacognitive Interpersonal Therapy, which included: creating a shared formulation of his paranoid attitudes; trying to change his inner self‐image of self‐as‐inadequate and his interpersonal schemas where he saw the others as threatening. Guided imagery and rescripting techniques, coupled with behavioral experiments, were used to promote a change. At the end of the therapy the client reported a reliable change in general symptomatology and, specifically, in interpersonal sensitivity, hostility, and paranoid ideation; he could no longer be diagnosed as PPD and only some paranoid and antisocial characteristics remained.