Drawing on the natural resource-based view and coordination theory, this study examines the extent to which different combinations of internal and external green supply chain management (GSCM) practices influence third-party logistics providers' (TPLs) operational and financial performances. A fuzzy-set qualitative comparative analysis of survey data from 232 TPLs shows that combined internal and external GSCM practices improve both operational and financial performances. However, taking into account the TPLs' size allows alternative combinations of GSCM practices: a combination of green supply and eco-design packaging improves small TPLs' performances, whereas a combination of all GSCM practices, except investment recovery and reverse logistics, improves large TPLs’ performances. By using fuzzy-set qualitative comparative analysis instead of traditional linear methodologies, this study offers a new approach to determine the configurations of internal and external GSCM practices that lead to enhanced operational and financial performances in TPLs, rather than treating each GSCM practice separately.