The purpose of this study is to verify the impact of international financial reporting standards (IFRS) adoption on the quality of accounting performance and efficiency of investment decisions in the Saudi business environment as an emerging economy. In this study, content analysis approach is adopted for examining the annual reports of Saudi companies listed in Saudi stock exchange market during two periods: the pre-adoption of IFRS period during the year of 2016 and the post-adoption of IFRS period during the period 2017-2018. The study uses accounting information, accounting conservatism, earning management as alternative variables of accounting performance quality. In addition to accounting profit quality, liquidity and cost of capital are also used as alternative variables for the efficiency of investment decisions. The study finds that there was a positive impact of IFRS adoption on the quality of accounting performance, since it was positively related to both the qualitative characteristics of information and accounting conservatism, while it was negatively related to earning management. IFRS also improves the efficiency of investment decisions, as it was positively related to both profit quality and liquidity while it was negatively related to cost of capital.