Existing and dominant perspectives on determinants of firm internationalization have focused on the firm-specific and country-specific factors, paying less attention to the question if and how can clusters foster internationalization of cluster firms'. To investigate this issue, we conducted the study focused on the Polish clusters. First, we conceptualize the impact of clusters on the internationalization of cluster firms by introducing the concepts of the propensity of internationalization and intensity of internationalization. Second, we assess the internationalization intensity of clusters in Poland and check how cluster managers facilitated the internationalization of cluster firms. The results obtained show that clusters play an important role in neutralizing the liability of foreignness suffered by cluster entities. The findings confirm that the need of internationalization which is related to the internationalization propensity emerges over the time as a cluster matures and internationalization intensity is higher in case of more dense clusters. By combining meso- and microeconomic perspectives, this study offers a more holistic approach for studying internationalization processes.