In the last decades, the concept of cluster has gone through the vast conceptual development, resulting in its various definitions and categories – ‘cognitive clusters’, ‘learning clusters’, ‘creative clusters’, ‘working cluster’, ‘effective cluster’ (Capello & Nijkamp, 2019; Martin & Sunley, 2003; Lagnevic et al., 2004). Despite of their different approaches all above definitions share one common ‘relational’ context. Starting from the Porterian concept of ‘industry cluster’ as spatial networks of industries, which enjoy positive externalities from co-location and frequent interactions, to the more recent concept of a ‘working cluster’, where firms and other organizations maximize benefits from the synergetic effects coming from integration, cooperation, and competition (Porter 2008). Furthermore, Bochniarz-Faoro refer to ‘effective cluster’, which is characterized by the rich social networks that enables all participants to efficiently cooperate with one another (2016). Social networks have been also recognized as underlying factor for cluster development in other studies, including Phillips (2006), Ostergaard (2009). Nevertheless, the inherent complex configuration of every cluster, and its divergent patterns of evolution make it difficult to determine the mechanism of Social Capital formation and its impact on cluster growth. To identify this dependency a more case by case analysis maybe useful. The study aims to explore and evaluate the role of social capital in the evolution of a cluster, using the example of the life sciences industry. Social Capital is defined here as a capital that results from investments in building relations, institutions and networks that produce collaborative attitudes, shared values, mutual understanding and trust. The notion evolution refers here to gradual transition from an emerging cluster to a functioning and growing cluster during the growth phase of markets. More specifically, the study takes an example of five life sciences clusters – San Francisco Bay Area (US), Cambridge (UK), Copenhagen-Lund (Denmark/Sweden), Seattle (US) and Poland, to answer: How does notion of Social Capital and its different dimensions operate within clusters’ evolution? What is the contribution of Social Capital within different stages of clusters’ evolution? Does Social Capital and social networks can exert a distinct influence on the performance of different clusters? What types of social networks induce cluster related positive externalities?