Purpose - Organizational ambidexterity enables firm to simultaneously exploit existing resources and explore new resources. It is associated with high levels of organizational performance. This paper identifies key internal management resources which contribute to building organizational ambidexterity. In particular, this study examines the impact of intellectual capital, i.e. human, social and organizational capital, on organizational ambidexterity which in turn influences firm performance. Design/methodology/approach – The research is conducted within the context of professional service firms (PSFs) due to the importance of intellectual capital and organizational ambidexterity. Data was collected from 112 Chinese (cross-sectional design) and 93 Irish accounting firms (time-lagged design). Findings – Results provide support for the linkage of intellectual capital to organizational ambidexterity and firm performance. Interestingly, findings are mixed regarding the impact of the three types of capital resources on organizational ambidexterity across both countries. Research implications - The results showed that the three types of intellectual capital influenced organizational ambidexterity differently for Chinese and Irish PSFs. Consistent support was found for an association between organizational dexterity and firm performance in both contexts. Whilst we cannot infer directly that human capital wasn’t important than social and organizational capital in the Chinese context compared to the Irish context, it would seem that that may well be a cultural imprint on the antecedents of organizational ambidexterity. Practical implications - This study finds that various components of intellectual capital facilitate organizational ambidexterity which in turn improves firm performance. Therefore we provide managers with evidential support for the salience of intellectual capital in enabling organizations to simultaneously engage in exploiting existing resources while also exploring new ideas and opportunities. Originality/value – This study is unique in that it highlights the importance of internal management resources in building up organization’s ambidexterity capability. The link between intellectual capital and organizational ambidexterity was established using a rigorous research design which has not been done before. It also emphasizes the role of people in leading to organizational effectiveness via developing organizational ambidexterity. Furthermore the evidence is gathered in two countries.