What factors motivate firms to improve quality management and enter customer–supplier collaborative relationships? This study investigates how the pressure to adopt the ISO 9000 or 14000 series from downstream customers affects customer–supplier collaborations and process improvement. Employing a survey dataset linking respondents (i.e., focal firms), their downstream customers, and their upstream suppliers in Indonesia, the Philippines, and Thailand, this study finds that the ISO requirements to the suppliers promote the development of collaborative relationships between the focal firms and their suppliers and improve process control. Regression analysis and csQCA indicate importance of analyzing combinations of the factors rather than individual factors that may affect quality control improvement.