This paper tests the impact of firms’ ownership structure on firms’ innovation decisions using a rich dataset of about 20,000 Italian manufacturers. After accounting for its possible endogeneity, we find that ownership concentration negatively affects the probability of innovation, especially by reducing firms’ R&D effort. The analysis reveals that conflicts of interest between large and minority shareholders are a determinant of the negative effect of ownership concentration on innovation. Moreover, risk aversion induced by lack of financial or industrial diversification appears to be an additional source of large shareholders’ reluctance to innovate. Once we distinguish across types of shareholders, we uncover some evidence that families support innovation more than financial institutions, but that the benefits of financial institutions for technological change increase with their equity stakes. Collectively, the findings suggest that innovation is a channel through which agency problems among shareholders influence firm performance. (This abstract was borrowed from another version of this item.)