The present paper analyses the potential relationships among collaboration within different companies for innovation purposes, organizational learning and product innovation. In this vein, we empirically argue that companies need to develop knowledge management procedures in order to transform this inter-organizational collaboration in new products or processes. Structural equation modelling was employed to test the hypotheses in a sample of 451 Spanish companies. Although previous researches have partially provided theoretical models that associate organizational learning with innovation, few empirical studies consider that organizational learning could mediate the relationship between collaboration and product innovation. Results provide strong evidence about the relationship between inter-organizational collaboration and innovation in companies. It also shows that collaboration has a positive impact in the various knowledge management phases and that organizational learning mediates the relationship between collaboration and innovation. These results support the previous literature maintaining the importance of developing external relations for the promotion of innovation in the company, according to open innovation models. Likewise, our results indicate that managers need to reinforce the processes of knowledge management in their companies, since they are key competencies for generating innovations.