Grounded in self-determination theory (Deci & Ryan, 1985), the purpose of the present study was to examine whether amotivation, self-determined and controlling types of motivation could predict a range of exercise-related behaviours, cognitions and physical self-evaluations. Exercisers (n = 375) from ten health clubs in the North of England completed questionnaires measuring exercise motivation, exercise stages of change, number of relapses from exercise, future intention to exercise, barriers self-efficacy, physical self-worth and social physique anxiety. Controlling for age and sex, multiple and logistic regression analyses supported our hypotheses by showing self-determined motivation (i.e. intrinsic motivation and identified regulation) to predict more adaptive behavioural, cognitive and physical self-evaluation patterns than external regulation and amotivation. Introjected regulation was related to both adaptive and maladaptive outcomes. Furthermore, a multivariate analysis of variance revealed that exercisers in the maintenance stage of change displayed significantly more self-determined motivation to exercise than those in the preparation and action stages. The results illustrate the importance of promoting self-determined motivation in exercisers to improve the quality of their experiences, as well as to foster their exercise behaviour. Future research should examine the mechanisms that promote self-determined motivation in exercise.