Today, the impact of intellectual capital is interesting for the scholars worldwide regarding the performance of the organizations, and knowledge comprises its primary core. Optimal use of knowledge contributes to explore needs of clients, leading to innovation and new valuable opportunities. Qualitatively improved services in the libraries of hospitals realizes through taking human capital and their optimal use of knowledge into consideration. The present study investigated the relationship between optimal use of knowledge and intellectual capital among library managers of public hospitals in Tehran. This study is a descriptive-correlation applied research holding all of the library managers of public hospitals in Tehran as the statistical population. The data collection was carried out via Bontis Intellectual Capital Questionnaire (2004) and Bukowitz & Williams Knowledge Management Questionnaire (1999). Cronbach's alpha was employed to measure the internal consistency reliability among the items and found at over 70%. To analyze the statistical data, the Pearson Correlation Test was used. The results showed that there were not any significant relationship between optimal use of knowledge and human resource capital and structural capital components (P>0.05). On the whole, between intellectual capital and optimal use of knowledge there is a significant relationship (P<0.05).The data analysis revealed that there is a positive and direct significant relationship with low intensity between optimal use of knowledge and intellectual capital among library managers of public hospitals in Tehran. In other words, the Foucault theory of power relation is confirmed