Purpose This research aims to reveal the impact of Green Performance Appraisal (GPA) on Organizational Sustainability (OS) and to explore the effect of GPA on Employee Green Behavior (EGB). Moreover, it investigates the factors underlying the relationship between GPA, EGB and OS. Further, it intends to examine the role of Green Knowledge Usage (GKU) in the relationship between EGB and OS. Design/methodology/approach Partial Least Squares Structural Equation Modelling technique, SPSS and the Smart PLS 4 Software were used to test the hypotheses and the data collected via a cross sectional online survey conducted among Lebanese firms registered in the local chamber of commerce. Findings The results show that GPA plays a significant role in enhancing EGB and in promoting OS. It proves also that EGB partially mediates the relationship between GPA and OS. Further, it reveals the moderating role of GKU in reinforcing the relationship between EGB and OS. Research limitations/implications Although the study has some limitations related to the limited sample targeted and the cross-sectional data used, the findings provide various managerial implications and help in enhancing OS. It also advances green human resources management practices theoretically and practically. Originality/value This research aims to fill the gaps observed in the literature and explores the impact of GPA on OS examining the mediating role of EGB and the moderating effect of GKU.