Purpose: The objectives were to develop and validate the Coaches' Interpersonal Style Questionnaire. The Coaches' Interpersonal Style Questionnaire analyzes the interpersonal style adopted by coaches when implementing their strategy of supporting or thwarting athletes' basic psychological needs. Method: In Study 1, an exploratory factor analysis was performed with 265 Spanish male athletes, between 11- and 17-years-old, to confirm the internal structure of the questionnaire. Study 2 was conducted with 430 athletes, also between 11- and 17-years-old. Both confirmatory factor analysis and exploratory structural equation modeling were used to test a set of alternative models to find the best measurement model. Results: The hierarchical exploratory structural equation modeling model showed the best fit to the data and acceptable standardized factor loadings. Concurrent validity was revealed through correlational analysis of the basic psychological need satisfaction and frustration. Conclusion: This study provides a multi-dimensional questionnaire to assess coaches' interpersonal style perceived by athletes.