This study aims to clarify aspects of interactions by using rhythmic movements among children under two years of age in a nursery school. We employed the concept of communicative musicality advocated by Malloch and Trevarthen (2009) as the theoretical framework for this study. The naturalistic observations were conducted in the nursery school classroom during the free play time allocated to the children. Three scenes in which children interacted with each other by using rhythmic gestures were extracted; these gestures were analyzed by employing episode analysis and movement analysis using ELAN. The results revealed that the children shared the musicality and emotion inherent the rhythmic movements of their partner and attempted to co-create a narrative. In order to establish interaction based on communicative musicality with rhythmic movements, attracting the intended person’s attention is a prerequisite; however, the study results show that it may be difficult for children of this age to become aware of this prerequisite, thus hindering establishment of their communication with their peers. The results also suggest that the intervention of a common object or matter enables children to understand the rhythmic movements’ inherent meaning.