Employing a sample of Vietnamese banks covering the period 2005 to 2015, this study investigates the influence of partial, and selective, financial liberalisation on bank efficiency by ownership type in a transition economy. The key findings are: (1) state-owned banks outperformed all other ownership types; (2) selective privatisation of state-owned banks exerted a positive influence on bank efficiency; (3) rural-to-urban private bank transformation decreased banking system efficiency; (4) minority foreign ownership exerted an insignificant impact on bank efficiency; (5) business group ownership improved the provision of intermediation services but deteriorated overall bank operating efficiency. Overall, the findings suggest that the post-WTO partial-liberalisation of the banking system in Vietnam impacted banks' efficiency differently subject to ownership type, with potentially adverse implications for long term economic growth and development.