Collaboration in green product innovation (GPI) is becoming increasingly important, and research on such innovation has grown in recent years. This study reviews literature on external collaborations in GPI to investigate drivers, inter‐organizational factors and intra‐organizational factors for such collaborations. The review includes a total of 67 papers. Survey studies and case studies are the methodologies applied most in the reviewed papers. The most common collaborators are suppliers and customers. Drivers include economic factors, regulations, customer demand, competitiveness and firm performance. Numerous inter‐organizational collaboration factors are presented and summarized in terms of partner selection, relationship management, knowledge access and agreements. Intra‐organizational factors mainly concern cross‐functional collaboration, capabilities and internal practices. Implications for policy and practitioners are presented. Copyright © 2017 John Wiley & Sons, Ltd and ERP Environment