This paper aims to examine the impact of liberalization in 2009 on the determinants of bank efficiency in Malaysia by employing a two-stage approach within the context of the growing number of foreign commercial banks. Commercial banks can play a vital role in the internationalization and diversification of Malaysia's financial sector. In the initial stage, measuring the efficiency score of 19 commercial banks throughout 2008 to 2019 by using the Data Envelopment Analysis (DEA). Multivariate panel regressions were then used to determine the impact of liberalization on the determinants of bank efficiency in 2009. As a result, domestic commercial banks seem to be more competitive than their foreign counterparts. The findings signify that bank size, market power, capitalization, and liquidity all have a positive impact on technical efficiency. However, credit risk, bank diversification, and inflation all have a negative impact. The control of the effects of liberalization, bank size, capitalization, bank’s market power, and liquidity remain positive. However, bank diversification and inflation flip negative to positive, whereas credit risk becomes less explanatory. The findings will provide bank stakeholders, regulators, investors, and regulators with important insights into the impact of liberalization measures on bank efficiency and its determinants.