Several investigations are commonly found in marketing literature but there are relatively few theoretical and empirical researches that associate marketing with corporate social responsibility (CSR). There are even less empirical investigations that relate these two important constructs with firm reputation of enterprises aimed to small and medium-size enterprises (SMEs) which shows a clear void in literature regarding the existing relation between CSR activities, brand image of products or services created by enterprises and their firm reputation. For this reason, the main objective of this research paper is the analysis of the existing relation between CSR activities, firm reputation and brand image of products or services of SMEs by using a sample of 308 enterprises from Aguascalientes State. The results obtained show that CSR activities have positive and significant effects in both the firm reputation and brand image of products or services created by SMEs.