Perceptions and evaluations of the own body are important sources of self-esteem. Having a rheumatic disease challenges maintenance of positive self-esteem due to consequences of the disease such as unfavorable sensations as pain and limited (physical) functioning. We expect that a positive experience of the own body in spite of a rheumatic disease (body-self harmony) will be associated with higher levels of self-esteem and that experiencing the body as unworthy part of the own person or as disabler for own strivings (body-self alienation) will result in lower levels of self-esteem. For this explorative study, the body experience questionnaire (BEQ) measuring body-self unity was developed and piloted. One hundred sixty-eight patients visiting the outpatient rheumatology clinic of the Medisch Spectrum Twente, Enschede, The Netherlands, completed a questionnaire on touchscreen computers to measure body-self unity (BEQ), illness cognitions (illness cognition questionnaire), pain intensity, functional limitations (health assessment questionnaire disability index), self-esteem (Rosenberg Self-Esteem Scale) and demographics. To analyze predictors of self-esteem, hierarchical regression analyses were employed. The BEQ revealed a two-factor structure with good reliability (subscale harmony, four items, Cronbach's α = 0.76; subscale alienation, six items, Cronbach's α = 0.84). The final model of the hierarchical regression analyses showed that self-esteem can be predicted by the illness cognitions helplessness and acceptance, by harmony and most strongly by alienation from the body. R(2) of the final model was 0.50. The relationship between functional limitations and self-esteem was totally mediated by the psychological constructs body-self unity and illness cognitions. This explorative study showed the importance of the unity of body and self for self-esteem in patients with a rheumatic disease.