Phenothiazine‐induced lupus with circulating anticoagulant (CAC) has been reported infrequently, and is rarely associated with significant symptoms. We describe a patient who we suspect had perphenazine‐induced lupus erythematosus with CAC. She had recurrent episodes of venous thrombosis and ultimately developed superior vena cava syndrome. The relationships among phenothiazine‐induced lupus, CAC, and thrombosis are discussed.