This study examined arthritis self-efficacy and self-efficacy for resisting eating as predictors of pain, disability, and eating behaviors in overweight or obese patients with osteoarthritis (OA) of the knee. Patients (N = 174) with a body mass index between 25 and 42 completed measures of arthritis-related self-efficacy, weight-related self-efficacy, pain, physical disability, psychological disability, overeating, and demographic and medical information. Hierarchical linear regression analyses were conducted to examine whether arthritis self-efficacy (efficacy for pain control, physical function, and other symptoms) and self-efficacy for resisting eating accounted for significant variance in pain, disability, and eating behaviors after controlling for demographic and medical characteristics. Analyses also tested whether the contributions of self-efficacy were domain specific. Results showed that self-efficacy for pain accounted for 14% (p = .01) of the variance in pain, compared to only 3% accounted for by self-efficacy for physical function and other symptoms. Self-efficacy for physical function accounted for 10% (p = .001) of the variance in physical disability, while self-efficacy for pain and other symptoms accounted for 3%. Self-efficacy for other (emotional) symptoms and resisting eating accounted for 21% (p < .05) of the variance in psychological disability, while self-efficacy for pain control and physical function were not significant predictors. Self-efficacy for resisting eating accounted for 28% (p = .001) of the variance in eating behaviors. Findings indicate that self-efficacy is important in understanding pain and behavioral adjustment in overweight or obese OA patients. Moreover, the contributions of self-efficacy were domain specific. Interventions targeting both arthritis self-efficacy and self-efficacy for resisting eating may be helpful in this population.