The research aims to measure the impact of the efficiency of investment decisions in the Iraqi companies listed in the Iraqi Stock Exchange, and this goal is achieved by identifying the concept of the efficiency of investment decisions, by relying on the data of the annual financial reports of a sample of Iraqi companies listed in the Iraqi Stock Exchange, which numbered (27 companies represented by (15) companies from the banking sector, (8) companies from the industrial sector and (4) companies from the insurance sector for the period from (2011-2020). For the purpose of measuring the efficiency of investment decisions, a model (Mcnichols & Stubben, 2008) was used, and the research reached several results, the most important of which is that there is an efficiency of investment decisions in Iraqi companies listed in the Iraqi Stock Exchange. The most important thing recommended by the researcher is the necessity of focusing and paying attention to the factors that result in the efficiency of investment decisions, such as the quality of accounting information and reliance on the International Financial Reporting Standards (IFRS), as well as the study and analysis of financial data for making investment decisions in a detailed manner and following the methods of evaluating investment projects (economic feasibility study).) to prevent making wrong (sub-optimal) investment decisions that result in huge irreversible losses.