Abstract This study analyzes the influence of composition of the Board of Directors and their social relations (board interlocking) on performance of Brazilian companies. A descriptive study based on documentary research was conducted with a total of 1,163 companies' observations and 18,119 standardized observations regarding directors. Simultaneous equations were applied to the data analysis. The survey results showed that, regarding the influence of composition of the Board of Directors on the performance of the companies, among variables used to identify its characteristics, that some showed endogeneity. Among the characteristics of the Board of Directors, the duality of the board was exogenous when comparing market performance (Tobin's Q) and the outsiders were also exogenous for internal performance (Return on Equity). Thus, the duality of the board is more influenced by the specificities of each company than by the market value of the companies. The characteristic outsiders are more influenced by the institutional environment than by the ROE. The practice of board interlocking proved to be insignificant in relation to the market value, indicating natural selection. Therefore, it is not possible to infer that the board interlocking can increase the dependency of the management, compromising the role of monitoring. Also, it is not possible to state that better positioned and central companies in the corporate relationships network show better performance.