["Corporate Social Responsibility and Environmental Management, EarlyView. ", "\nABSTRACT\nUrgent environmental challenges require solutions that transform production, delivery, and consumption processes. The literature identifies collaboration with external stakeholders as critical for effective environmental innovation (EI), particularly among international firms that leverage global resources. Drawing on the open innovation (OI) perspective, we examine how configurations of external cooperation partners shape EI and influence internationally operating firms. Specifically, we analyze how OI and EI affect firms' ability to coordinate and synchronize networks to increase foreign sales. Using data from the Community Innovation Survey (CIS) 2014 for 891 Portuguese firms, we apply crisp‐set Qualitative Comparative Analysis (csQCA) to identify configurations of cooperation partners associated with EI and complement this analysis with logit regression. The results reveal six equifinal paths to high EI performance and show that combining science‐driven collaboration with upstream research can hinder eco‐innovative efforts and reduce firms' internationalization. We provide a theoretical explanation for this counterintuitive finding and contribute to the data on the adoption of open environmental innovation (OEI) by international firms.\n"]