As part of their business strategies, companies seek to legitimize themselves before their interest groups through their social responsibility activities. These strategies should allow them to compete in the market every time they position their image and their financial performance increases. Therefore, the objective of this research is to analyze social responsibility and explain how it contributes to the construction of the organizational legitimacy of large Mexican companies, and to measure whether said legitimacy generates an impact on financial performance. The research is non-experimental quantitative, cross-sectional correlational, the hypotheses of this study were verified through a structural equation model (SEM) with the use of the Smart-PLS statistical tool. The study population was Mexican companies that are socially responsible, that are listed on the Mexican Stock Exchange and that publish their financial results through sustainability reports. The data was collected through an adapted instrument, managing to collect information through a convenience sample, that is, without considering financial companies, applied to a sample of 39 companies. Among the findings, it is shown that corporate social responsibility measured through its three main dimensions (economic, social and environmental) explain the organizational legitimacy built by the companies on the Mexican Stock Exchange and that said legitimacy also has a positive impact on their financial performance as a result of said legitimacy.