This study is to study the relationship between market orientation and firm performance by considering the mediating role of management accounting systems in pharmaceutical companies listed on the Tehran Stock Exchange. Using the research method, a descriptive correlational survey was conducted based on a standard questionnaire, which is cross-sectional in terms of time and is practical in terms of purpose. The statistical population of this research is financial managers and senior accountants of pharmaceutical companies with 95 people for the second half of 1398. The statistical sample is 76 people based on Cochran's formula. In order to achieve the research objectives, this information was analyzed using SPSS 26 software and also the diagram of structural equations using Smart PLS software by applying appropriate statistical tests according to the research hypotheses. Market orientation has a positive and significant effect on management accounting systems. The data obtained from the study indicate a positive and strong correlation between these variables. Also, Pearson correlation coefficient is 0.659 and the level of significance is below 50%, which has a significant and positive relationship. It shows that increasing one increases the other. Management accounting systems have a positive and significant effect on the company's performance. The data obtained from the study indicate a strong and positive correlation between these variables, also Pearson correlation coefficient of 0.752 and a significance level below fifty percent. Which shows a significant and positive relationship, that is, the increase of one causes the increase of the other. This is management accounting that creates the knowledge base for internal users and forms the information flow for definitive management. It is suggested that in companies, strategic management accounting systems use company costs that are used in practice. Analyze and take steps to inform stakeholders of the costs incurred. Managers are encouraged in the company to take creative initiative in the market to enter emerging markets to attract creative ideas. Take.