Although successful collaborative learning requires socially shared metacognitive regulation (SSMR) of the learning process among multiple students, empirical research on SSMR is limited. The present study contributes to the emerging research on SSMR by examining its correlation with both collaborative learners' content processing strategies and the level of transactivity in their discussions. The study is, more specifically, conducted in an authentic higher education reciprocal peer tutoring (RPT) setting. All sessions of a semester-long RPT-intervention of five randomly selected RPT-groups were videotaped (70 h of video recordings). Literature-based coding instruments were developed to analyse RPT-groups' SSMR, content processing strategies (i.e., questioning and explaining), cognitively-oriented and metacognitively-oriented transactive discussions. In order to examine how RPT-groups' SSMR is related to their content processing and transactive discussions, binary logistic regression analyses were conducted. The results indicate that both questioning and explaining are positively associated with SSMR. Especially deep content processing shows a strong relationship. Further, both cognitively-oriented and metacognitively-oriented transactive discussions significantly increase the probability of RPT-groups engaging in SSMR. More specifically, transactive discussions in which RPT-participants elaboratively operate on each other's metacognitive regulation appear to be conducive. In contrast, non-transactive discussions are not significantly associated with SSMR.