This study aims to examine the impact of minority investor protection mechanisms on agency costs. All relevant indicators of minority investor protection adapted from the World Bank’s annual ‘Doing Business’ reports, along with concentrated government ownership, are employed with a panel data sample of 135 Vietnamese listed firms during the period 2014–2018. It is found that the following mechanisms are effective in mitigating agency costs and hence agency problems at the firm level: 1) review and approval requirements for related-party transactions; 2) minority shareholders’ ability to sue and hold directors liable for their duties; 3) minority shareholders’ access to internal corporate documents; 4) investors’ rights to approve major corporate investment and sale of asset decisions; and 5) disclosure in annual reports of salaries, bonuses and other forms of remuneration to directors and management. Interestingly, board independence and controlling government shareholders are not confirmed to play significant roles in addressing agency problems. To the best of the authors’ knowledge, this is the first attempt at testing for the impact of minority investor protection mechanisms developed by the World Bank on agency costs at the firm level, hence providing empirical evidence for the adoption of the minority investor protection mechanisms promoted by the World Bank. This study also provides policy implications for selecting effective mechanisms to mitigate agency conflicts between controlling shareholders and minority investors in order to enhance the financial performance of firms in an Asian emerging market.