<p>Computer-supported collaborative learning (CSCL) has been widely studied over the past few decades; however, relatively little attention has been given to groups’ shared metacognitive processes in virtual collaborative learning settings. In particular, the role of transactive interactions in supporting socially shared regulation of learning (SSRL) remains underexplored. This study investigates the interplay between transactivity modes and SSRL phases, and examines how these patterns contribute to the development of shared understanding for task execution and knowledge construction. Participants were 38 higher education students who engaged in collaborative tasks over a six-week period using Microsoft Teams. Four case groups (two high-performing and two low-performing) were selected to explore the emergence and sequential patterns of transactivity and SSRL phases. Video recordings from 29 collaborative sessions were analysed using qualitative content analysis and process mining. The findings reveal distinct patterns of transactivity during the forethought and performance phases of regulation in high- and low-performing groups, highlighting the regulatory functions of different transactivity modes. The results suggest that transactive interaction supports not only social-cognitive processes, such as the development of shared understanding, but also the shared metacognitive processes required for groups to achieve common learning goals in virtual collaborative learning environments.</p>