Several industries are in the maturity stage of their life cycle, but very little attention has been devoted to their study. Past research reveals that an entrepreneurial strategic posture may be most strongly associated with performance in emerging industries, rather than in mature ones: successful organizations adopts a more conservative strategic posture in mature industries. However, anecdotic evidence shows the cases of companies that have been successful in these industries just because of their entrepreneurial posture, and studies have been carried out to explore their entrepreneurial processes. Thus, the main objective of this study is to explore the relationship between firm-level entrepreneurship and performance of companies operating in mature industries. The research problem is approached by studying firm-level entrepreneurship in its content (product development, market development and diversification) rather than in its process (entrepreneurial orientation). Moreover, we adopt a knowledge-based view of the firm and entrepreneurship: firm-level entrepreneurship is conceived as a knowledge-based behavior, whose dynamics have not been explored in the context of mature industries, as far as concerns the sharing of knowledge between companies and the types of knowledge needed.