The development of the circumplex model for coach behavior recently provided researchers an integrative model to assess coach behavior. While the circumplex model has currently only been deployed in cross-sectional research designs using the Situations in Sports questionnaire (SISQ), it has clear potential within research on dynamics of coach behavior. However, the SISQ consists of vignette-based situations and is too extensive for such frequent administrations. Within the present study we therefore developed the Coach Behavior in Sports Questionnaire (CBSQ), a 32-item alternative for the SISQ which consists of general items rather than vignette-based situations. First, content validity of 54 initial pilot CBSQ items was tested in a sample of 34 expert coaches. Second, construct validity, predictive validity, and reliability of the 32-item CBSQ was tested in a sample of 689 athletes and 420 coaches. Third, within-person variability of coach behavior was longitudinally assessed using the 32-item CBSQ during a five-week training and game period in a sample of 31 coach-athlete dyads. The 32-item CBSQ showed to be a valid and reliable alternative for the SISQ. Also, coach behavior showed considerable within-person variability over the five-week period in all coaching styles and approaches. Additionally, a 24, 16, and 12-item version were tested to provide even shorter alternatives. The CBSQ opens new horizons for future longitudinal research and coach reflection programs based on the circumplex model for coach behavior. •We replicated the circular structure of the circumplex model for coach behavior.•The CBSQ showed to be a valid and reliable questionnaire to assess coach behavior.•Coach behavior fluctuates both on between-person and within-person level.•The CBSQ can be used to assess coach behavior within future longitudinal studies.