This study investigates how firm innovation is jointly influenced by two levels of collaboration. At the interorganizational level, collaboration via interfirm alliances and joint ventures is an important method for accessing external knowledge and information. At the intraorganizational level, intrafirm collaboration among R&D scientists is a significant mechanism for knowledge transfer and diffusion. Both forms of collaboration are known to influence firm innovation, but little is known about their joint impact. I argue that interorganizational collaboration provides an opportunity for absorbing new knowledge while intraorganizational collaboration networks shape a firm's ability to use and exploit this information. A longitudinal study on almost fifty medical device firms over a fifteen year period shows that the positive effect of interfirm R&D alliances on firm innovation is stronger for firms with better connected intrafirm collaboration networks, whereas the presence of strongly-connected groups within a firm weakens this relationship. These results suggest that firm innovation is the outcome of a multilevel network process in which interfirm ties are complemented by intrafirm networks.