This paper analyses the effect of market structure on profitability and stability using the sample of 130 commercial banks in ASEAN-5 countries (Indonesia, Malaysia, Philippines, Singapore and Thailand) over the period from 2001 to 2013. More specifically, this study investigates the relevance of the structure conduct performance (SCP) and the relative market power (RMP) hypotheses. This paper also examines the relevance of ‘concentration-stability’ and ‘concentration-fragility’ hypotheses in the case of ASEAN-5 banking. In doing so, we control for the effect of bank-specific and country-specific factors. Empirical results based on system-generalised method of moments (GMM) analyses support the RMP hypothesis but fail to support the SCP hypothesis. We find that concentration stabilizes the banking sector. Evidence also highlights the importance of bank-specific controls related to capitalization and costs on profitability and stability. Implications for policy-makers are addressed.