Although the importance of boundary spanning in blended and online learning is widely acknowledged, most educational research has ignored whether and how students learn from others outside their assigned group. One potential approach for understanding cross-boundary knowledge sharing is Social Network Analysis (SNA). In this article, we apply four network metrics to unpack how students developed intra- and inter-group learning links, using two exemplary blended case studies in Spain and the UK. Our results indicate that SNA based upon questionnaires can provide researchers some useful indicators for a more fine-grained analysis how students develop these inter- and intra-group learning links, and which cross-boundary links are particularly important for learning performance. The mixed findings between the two case-studies suggest the relevance of pre-existing conditions and learning design. SNA metrics can provide useful information for qualitative follow-up methods, and future interventions using learning analytics approaches.