Self-efficacy is a psychosocial determinant of physical activity in adults. Different scales have been used to measure physical activity self-efficacy. This review examines the theoretical and measurement quality of scales measuring physical activity self-efficacy in physical activity-promoting interventions. The search strategy was based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Studies were included if they measured physical activity self-efficacy in adults aged 18 to 65. One hundred sixteen studies were reviewed. Fourteen multi-item and five single-item scales were identified. The properties of the scales varied. The following issues were identified: (a) a lack of concordance between self-efficacy and physical activity measurement, (b) not specifying physical activity levels, (c) theoretically imprecise construct labels, (d) not emphasizing essential conceptual properties, (e) not reporting dimensionality and (f) the use of single-item measures. The scales showed good administrative properties. Recommendations are made to improve the measurement of physical activity self-efficacy.