Purpose: This study examines the effect of profitability on financial sustainability while investigating the dual role of agency cost as a mediator and moderator among publicly listed non-financial companies in Indonesia, Malaysia, and the Philippines from 2020 to 2024.
Research Methodology: This quantitative study employs secondary panel data from 581 publicly listed non-financial companies, producing 2,905 firm-year observations. Financial data were obtained from Bloomberg and analyzed using Stata through fixed-effects panel regression with Driscoll–Kraay robust standard errors.
Results: The findings show that profitability enhances financial sustainability and reduces agency costs. Agency costs negatively affect financial sustainability and partially mediate the relationship between profitability and sustainability. However, agency costs do not moderate this relationship, indicating that it functions as a transmission mechanism rather than a boundary condition.
Conclusions: This study extends agency theory by demonstrating that agency costs primarily explain how profitability contributes to long-term financial sustainability. It also supports Signaling Theory by showing that profitable firms tend to demonstrate stronger governance quality and financial resilience.
Limitations: Agency cost is measured using a single accounting-based proxy, and its relatively small mediation effect (5.66%) and insignificant moderating effect limit the interpretation of its role in the relationship between profitability and financial sustainability. 
Contributions: This study contributes to the literature by integrating the mediating and moderating roles of agency costs within the profitability and sustainability framework. Practically, the findings provide insights for managers, investors, and policymakers to strengthen governance practices that support sustainable growth in emerging ASEAN markets.