This paper aims to address the gender imbalance in eco-innovation within firms, particularly focusing on the role of top managers. Drawing on Upper Echelon Theory and Social Identity Theory, the study investigates the influence of female CEOs on the promotion of eco-innovation and examines how knowledge factors influence this relationship, especially within transition countries. Using a comprehensive cross-sectional dataset from the World Bank and EBRD (BEEPS), the research analyses over 12,000 firms operating across 28 European and Central Asian transition economies. The findings show that firms led by a female CEO are less likely to engage in eco-innovation. However, the moderating effect of knowledge can complement CEO actions, though this effect varies by macro-area. The study suggests tailored strategies, emphasising the need for knowledge-sharing networks, targeted investments in human capital, and a collaborative organizational culture. These strategies represent concrete steps to enhance management capabilities and mitigating the costs and uncertainties associated with eco-innovation process in specific socio-economic contexts.