Changes in market structure or market concentration affect how companies behave and operate. In a more concentrated market, firms have more market power that allows them to remain inefficient without being forced out of the market. Also, regulations restricting banking activities and strict capital requirements are both related to less cost efficiency, but effective supervision and information sharing contribute to efficiency, hence the purpose of this research is to investigate the effect of competition and regulation of the banking market on the cost efficiency of banks and credit financial institutions. Accepted in Tehran Stock Exchange between 2015 and 2019 with a sample of 16 banks and credit financial institutions and using multivariable linear regression, the hypotheses were tested. In examining the significance of the whole model, considering that the significance level of the F statistic is less than 5%, the model is significant and the hypothesis of the F test is accepted at the confidence level of 95%. The coefficient of determination of the model also shows that 0.55% of the bank efficiency variable was explained by the explanatory variables. Also, the adjusted determination coefficient is equal to 0.43 percent. The results of the research showed that the competition and regulation of the banking market has a significant and adverse effect on the cost efficiency of banks and credit financial institutions accepted in the Tehran Stock Exchange.