Previous research on green product innovation (GPI) has primarily focused on the performance of new product development, neglecting the critical, early fuzzy front-end (FFE) phase. Drawing upon the firm's resource-based view (RBV) and dynamic capabilities perspective, this study explores how co-production affects FFE outcomes (creative idea and product definition proficiency) of GPI and whether joint learning ambidexterity is a mediating mechanism in international buyer-supplier relationships. Additionally, we provide a contingency perspective by considering the moderating role of the innovation ecosystem on the relationship between co-production and joint learning ambidexterity. Finally, this study contributes to a theoretical understanding, analyzing co-production as a predictor, joint learning ambidexterity as a mediator, and innovation ecosystem as a moderator.