External collaboration breadth is important for firms to acquire the knowledge needed to innovate. In this paper, we combine cross-sectional and longitudinal data from the Spanish Panel of Technological Innovation Survey (PITEC) to examine the indirect impact of R&D subsidies on firm external collaboration breadth. We contribute to understanding of the indirect impacts of R&D subsidies by first providing strong evidence of an economically significant average positive impact of R&D subsidies on firm external collaboration breadth. Second, our results advance understanding of the differential impacts of R&D subsidies by revealing the vast heterogeneity of the impact at the firm level, where approximately only half of treated firms experience a positive collaboration impact from R&D subsidies, while the remainder experience no impact or a negative effect. Finally, we advance understanding of the characteristics explaining the differential impact of R&D subsidies on external collaboration breadth by utilising the organisational learning literature to demonstrate the important role of firm collaboration experience.