Sustainability practices reflected in the concept of Environmental, Social, and Governance (ESG) are considered capable of reflecting the quality of corporate management as well as the long-term sustainability prospects of a business. One aspect within the governance dimension that has gained increasing attention is gender diversity on the board of directors, which is believed to influence the quality of decision-making and consequently affect corporate profitability and firm value. In line with this, several countries have established policies regarding the proportion of women on boards of directors to promote greater inclusivity. However, countries in the Southeast Asian region have not yet implemented specific written regulations governing the proportion of women on boards of directors. This condition motivates this study to examine the role of gender diversity in moderating the effect of ESG practices on firm performance in Southeast Asia. This study uses a sample of 83 companies from Indonesia, the Philippines, Thailand, and Vietnam during the 2020–2024 period. The independent variable is measured using ESG scores, while the dependent variables are measured using ROA to represent profitability and Tobin’s Q to represent firm value. The moderating variable is measured based on the proportion of women on the board of directors, after which the data panel test is conducted to determine the most appropriate regression model and hypothesis testing method. The result shows that gender diversity play a role in strengthening the effect of ESG practices on firm value, however it doesn’t give any effect in strengthening or weakening the relationship on firm profitability.