Corporate Social Responsibility (CSR) is generally associated to large firms, on which most of the theoretical and empirical studies have been oriented and published at the moment. In addition, there are relatively few studies focused on CSR in Small and Medium-sized Enterprises (SMEs). Moreover, even studies that relate this important construct in family SMEs are scarcer. In this sense, some researchers and academics have suggested that in family SMEs it is not possible to implement CSR, while another group of researchers consider that family SMEs are so by nature. Therefore, this research, using a sample of 297 family SMEs of Aguascalientes State (Mexico), aims to essentially identify CSR that this type of companies have. The results show that both social and environmental factor and economic factors are good predictors of CSR developed in family SMEs. Key Words: Corporate Social Responsibility, Family Firms, Small and Medium-Sized Enterprises.