OBJECTIVE: There is limited information about how morbidly obese osteoarthritis (OA) patients cope with the pain they experience. Pain catastrophizing is an important predictor of pain and adjustment in persons with persistent pain. This may be particularly relevant in the morbidly obese (body mass index [BMI] of 40 kg/m2 or greater) OA population at risk for increased pain. The present study first examined whether borderline morbidly obese and morbidly obese OA patients report higher levels of pain catastrophizing than a sample of OA patients in the overweight and obese category (BMI between 25 kg/m2 and 34 kg/m2). Next, it examined how pain catastrophizing is related to important indexes of pain and adjustment in borderline morbidly obese and morbidly obese OA patients.