Management in the banking industry is not solely focused on financial performance but also on the sustainability of their portfolios. To achieve this, banks need to incorporate sustainable finance into their balance sheet. In addition, a global phenomenon has emerged where investors have demanded the inclusion of sustainable finance in portfolios. This financial instrument served to support the global agreement on climate change, which they were committed to making a reality. The impact of sustainable finance on firm value remains a question. Therefore, this study aimed to examine the effect of sustainable finance and capital on firm value within the banking industry, focusing on entities listed on the ASEAN stock market from 2015 to 2021. To assess investor demand for involvement in sustainable finance, a moderating variable was included in the model. Furthermore, this study used a quantitative design and a purposive sampling technique with panel data regression analysis for the hypothesis testing. The results showed that sustainable finance and capital had a significant effect on firm value. Institutional ownership moderated the relationship between sustainable finance and firm value, although it did not moderate the link between capital and firm value. This indicated that banks prioritized sustainable finance due to its positive impact on their operations, ultimately leading to an improvement in firm value. Furthermore, institutional ownership influenced the relationship between sustainable finance and firm value, as banks strived to comply with international society or enhance firm value. This study incorporated profitability ratios and firm size as the control variables.