This article studies how knowledge management (KM) practices improve human capital. We conceptualize KM practices through six dimensions and test the relationship between each dimension and human capital. The empirical study which was carried out in Spanish firms belonging to the biotechnology and telecommunications industries shows that introducing KM practices has a positive impact on the improvement of human capital. In fact, firms that introduce practices related to continuous learning and the development of an innovative culture that encourages R&D projects improve the skills or abilities of their human capital.