Collaborative learning involves fluctuations in how students participate in social interaction and how they engage in interactions that are cognitive (e.g., sharing knowledge, monitoring learning) and more socio-emotional (e.g., encouragement, positive appraisal) in nature. Few studies have investigated how participation in social interaction fluctuates in relation to these varying types of interaction. The aim of this process-oriented study was to explore how actively students participated in cognitive and socio-emotional interactions and what characterized the moments when participation changed during transitions between the types of interaction. The qualitative analysis focused on video-recorded collaborative learning of six groups of student teachers (N = 24). We found that socio-emotional interaction involved more active participation than cognitive interaction. Changes in participation during transitions between types of interaction were characterized by shifts between domain-focused and metacognitive activities. Implications for supporting and studying productive social interaction in collaborative learning are discussed.