This study investigates how green supply chain management (GSCM) practices help translate the proactive environmental strategies (PES) of third-party logistics providers (TPLs) into enhanced economic and environmental performances. The survey data from 232 French TPLs suggest that the positive influence of PES orientations on environmental performance depends on the types of GSCM practices that are mobilised. More specifically, the study reveals that environmental performance is positively influenced by both eco-efficiency and eco-branding orientations through three main GSCM practices: distribution and transport, warehousing and green building, and reverse logistics. However, neither of these orientations influence environmental performance through two other GSCM practices: cooperation with customers and eco design and packaging, and only eco-efficiency orientations positively influence environmental performance through green supply. The study further suggests that an improved environmental performance helps TPLs increase their economic performance. Overall, this study offers interesting insights into the role of GSCM practices in managing TPLs’ PES orientations to improve their performances.