In this era of globalization, preventing organizations from undermining and degrading the environment has become a great challenge, especially when considering that organizations are among the major contributors to environmental deterioration. As a result, scholars have recently begun to focus on understanding the key determinants of employee green behavior (EGB), a nascent field within the area of sustainable development and organizational behavior. This study extends the emerging discussion over EGB by investigating how green behavior can be inculcated into employees’ mindsets and under what conditions this can best be accomplished. The present research examines the relationship between ethical leadership and EGB by the mediating mechanisms of green psychological climate, employees’ harmonious environmental passion, and employees’ environmental commitment, through the underpinnings of social learning theory. Further, the study examines the contingency effects of leaders’ pro-environmental attitudes to determine how leaders with ethical attributes and pro-environmental attitudes can create a green psychological climate that ultimately leads to EGB through employees’ harmonious environmental passion and employees’ environmental commitment. The approach to implementing theory development is deductive as the research employed a quantitative research design and survey administration with a time-lagged approach. Multi-level data were collected from 400 respondents working in public and private sector hospitals and universities in Pakistan. The analysis was conducted in MPlus. The results show positive and statistically significant effects of ethical leadership on EGB through the serial mediations of a green psychological climate and employees’ harmonious environmental passion, and a green psychological climate and employees’ environmental commitment. Moreover, the leaders’ pro-environmental attitude contingency strengthens the indirect impact of ethical leadership on EGB. This research provides several managerial implications through which organizations can strategically concentrate on EGB, including saving energy by turning off unused lights, reducing waste, and recycling.