The aim of this paper is to study the relations existing between the relational capital, both internal and external, and the firm financial performance. The investigation has been carried out on quantitative and qualitative data extracted from a sample of 100 Italian large firms. The paper deeply analyzes the dimension of the internal relational capital, not so widely studied in the literature. Findings demonstrate the influence of the internal relational capital (IRC) and of the external relational capital (ERC) on performance. The research suggests that an effort has to be devoted not only to improving relations with external stakeholders, but also to developing intra-firm relations. The research contributes to studies in management and in particular in internal organization by demonstrating that designing and implementing systems for supporting internal relation can improve firm performance.