Financial development plays a crucial role in shaping the trade–growth nexus by facilitating efficient resource allocation, technological adoption and risk management. However, empirical evidence on its role in the Association of Southeast Asian Nations (ASEAN) economies remains scarce. This study addresses this gap by investigating how financial development moderates the impact of trade openness on economic growth in ASEAN countries. Using the least squares dummy variable corrected estimator, our findings confirm that trade openness enhances economic growth. Notably, we identify a threshold level of financial development: below this threshold, insufficient financial development weakens the positive impact of trade openness, while beyond it, this negative moderating effect disappears. These findings highlight the need to strengthen financial markets to at least the threshold level, ensuring that financial development supports rather than hinders economic growth. JEL Classification: F43; F36; O16; C33; F15