Pathological forms of exercising are a topic of debate in terms of classification, etiology, and treatment. Validated instruments are a precondition for research in this field. The aim of this study was to validate the German version of the Commitment to Exercise Scale (CES-de). A confirmatory factor analysis was conducted using data from a large community sample (n = 571). In a second study, 100 eating disordered patients, 107 elite athletes and 100 individuals engaged in leisure time sporting activities were compared to assess discriminant validity and psychological correlates. A 1-factor solution showed the best fit to the data. The CES-de differentiated between the eating disordered group and individuals engaged in leisure time sporting activities, but not between those with an eating disorder and competitive athletes. The total score was significantly correlated with drive for thinness, perfectionism, and overall psychopathology. The CES-de can be considered a valid instrument for measuring problematic behavioral and attitudinal aspects of the commitment to exercise. The use of the CES-de total score is recommended. However, a more specific instrument should be used for athletes. A limitation of the study is that the samples were not stratified by age and gender.