This research aims to investigate the impact of International Financial Reporting Standards (IFRS) adoption and corporate governance mechanisms on investment efficiency. Further, this research also aims to investigate the impact of the interaction between IFRS adoption and corporate governance mechanisms on investment efficiency. This study uses a sample of 1,588 firm-years of data for manufacturing companies listed in the Association of South East Asian Nation (ASEAN) countries (Indonesia, Malaysia, Singapore, Thailand and Philippines) during the period of 2010 to 2012. The implementation of international accounting standards in the ASEAN region has developed among ASEAN countries in recent years. This study considers mechanisms of corporate governance at both firm and country level. IFRS adoption is measured using IFRS adoption scoring for each of the countries sampled. The empirical findings show that investment efficiency has been directly influenced by IFRS adoption level and mechanisms of corporate governance. However, the moderating role of IFRS adoption on the level of correlation between mechanisms of corporate governance and investment efficiency has not been proven in this study.