Today, competitiveness and maintaining competitive advantage is a condition for survival and a means to achieve optimal performance in companies. The performance of the company is one of the most important criteria for measuring the success of commercial companies, and along with financial resources, they are important indicators in the evaluation of an economic unit, which are used in financial decisions, securities valuation models, and methods of evaluating capital plans. Ai and... have a central role. On the other hand, due to the variety of customer demands, intense competition, globalization and financial weakness, businesses have become a more complex environment, which affects the performance and policies of different managers to deal with uncertainty and environmental changes. The purpose of this research is to investigate the effect of financial weakness on the dynamics, development and performance in the conditions of competitiveness and complexity of the companies' environment. Therefore, 147 companies admitted to the Tehran Stock Exchange in the years 2012 to 2014 were selected. To collect data and information, using the library method, by referring to financial statements, explanatory notes were made. In order to analyze the data, multivariate regression test and Eviuse software were used. The results showed that financial weakness has an effect on the development and performance of the company, the volatility of industry returns; In addition, the complexity of the companies' environment has a moderating role on the relationship between financial weakness, development and company performance. Also, the optimal management of cash and financial flexibility of companies in the competitive product market can lead to the preservation of valuable investment opportunities for companies, which ultimately leads to the improvement of the company's performance and value. be made