Good Corporate Governance and Firm Size as Determinants of Financial Sustainability: Financial Performance as Moderator

This study aimed to examine the effect of Good Corporate Governance and firm size on financial sustainability, with financial performance as a moderating variable, in Islamic commercial banks listed with the Financial Services Authority in Indonesia during the 2021–2025 period. The study employed a quantitative approach with an associative-causal design. The population consisted of all Islamic commercial banks registered with the Financial Services Authority, and a sample of 8 banks was selected through purposive sampling, resulting in 40 firm-year observations over five years. Secondary data were collected from annual reports and corporate governance reports. The data were analyzed using multiple linear regression and Moderated Regression Analysis with the assistance of SPSS version 25. The results showed that Good Corporate Governance had no significant effect on financial sustainability, with a significance value of 0.517. Firm size had no significant effect on financial sustainability, with a significance value of 0.125. Financial performance did not moderate the relationship between firm size and financial sustainability, with a significance value above 0.05. However, financial performance significantly and positively moderated the relationship between Good Corporate Governance and financial sustainability, with a significance value of 0.008 and an increase in the adjusted coefficient of determination from −0.015 to 0.143. These findings implied that the effectiveness of Good Corporate Governance in ensuring financial sustainability depended heavily on the bank's ability to generate healthy financial performance, while firm size alone did not guarantee financial sustainability in Indonesian Islamic commercial banks.