This paper studies the relative importance of individual inventors’ human capital and firms’ organizational capital in promoting a firm’s innovation output. We decompose the variation in innovation output into inventor- and firm-specific components. Inventors’ human capital is about 13 times as important as firms’ organizational capital in explaining a firm’s innovation performance in terms of patent counts and citations, while inventors’ human capital is only about the same as important when explaining the firm’s innovation styles in terms of patent exploratory and exploitive scores. In the cross section, inventors contribute more to innovation output when they are better networked, in firms with higher inventor mobility, in industries in which innovation is more difficult to achieve, and in publicly traded firms. Additional tests suggest that our main findings continue to hold after accounting for inventors’ endogenous moving. This paper highlights the importance of individual inventors in enhancing firm innovation and sheds new light on the theory of the firm.