Objective: This study set out to develop and validate a measure of primary health professionals' knowledge of counseling for weight management in adolescent patients in Indonesia. Methods: A literature review informed the development of an initial set of items. These were refined following content and face validity testing from expert panels. Item Difficulty Index and Discrimination Index were used to perform item analysis, and reliability (Cronbach α) was tested with 67 primary care practitioners from 30 out of Indonesia's 34 provinces. Results: An initial set of 114 questions was identified and arranged within three sections (healthy eating, physical activity, and behavioral change counseling skills). A series of validation processes resulted in 47 items with an acceptable Item Difficulty Index and Discrimination Index (0.2–0.9), and with sound internal consistency (Cronbach α coefficient 0.786). Innovation: This measure lays a foundation to evaluate future interventions to improve health professionals' capacity to address obesity within clinical practice. Conclusion: The developed questionnaire is a valid and reliable 47-item instrument to measure primary health professionals' knowledge of weight management counseling for adolescent patients. © 2026 The Authors