Several previous studies have investigated the effects of creativity and knowledge on innovation, both of them being considered prerequisites of innovation. However, the relationship among the different variables can be confusing due to redundant causality. In this paper, we study the influence of the mediating effect of creativity between breadth of knowledge (diverse sources of knowledge) and innovation by developing a conceptual model, and then test it on the Spanish ceramic cluster of Castellón. Empirical findings show that creativity is the mechanism through which the different sources of knowledge influence innovation. The implications of these results in relation to creativity, knowledge and innovation theory and practices are discussed.