Capital markets play an important role in the economy, because they direct the cash of people who cannot use their funds to those who can. Naturally, the good performance of these markets will be a key factor in ensuring economic growth, so if the capital markets are efficient, economic development will be realized. On the other hand, due to irrational decisions of investors, systematic errors have occurred in the capital market, and this problem causes the inefficiency of the market. The purpose of this article was to examine the role of irregularities in the decision making of investors in the country's capital market. In this study, a foundational data approach and statistical information collected from financial and economic experts in 1402 were used. The results obtained from this study indicated that the role of economic and financial components, market mechanism and executive functions, functions of institutions and financial and accounting components and the index of managerial and legal strategies in irregularities in capital decision making. It was 0.72, 0.55, 0.69 and 0.65 respectively. The results obtained from this study indicated that the criteria of cognitive ability and decision-making power of the experts of portfolio managers had a positive and significant effect on the investment efficiency. However, the entered criteria for behavioral bias such as representational bias and procrastination have led to a negative effect on investment returns.