We investigated the impact of environmental transformational leadership (ETL) on pro-environmental behavior (PEB) of employees in Kazakhstan. The study also examined the potential mediating effect of environmental awareness and green human resource management (GHRM) as a moderating effect, using the theory of planned behavior. An online cross-sectional survey was conducted with 268 Kazakh employees from private and public organizations. Structural equation modeling was used to test the theory-driven model. The results show that environmental leadership predicted employees’ PEB, environmental awareness mediated the relationship, and GHRM partially moderated the relationship. The results of bootstrapping tests reveal that environmental awareness played successive mediating roles in the link between ETL and PEBs, but the simple slope test did not support the moderating effect of GHRM. Environmental awareness and GHRM were identified as fundamental mechanisms that accounted for the connection between ETL and PEBs.