The purpose of the present study was to improve young learners' scientific understanding in CSCL environments. The study consisted of two phases: Phase I for fostering a collaborative learning culture, and Phase II for using Knowledge Forum as a CSCL tool. Primary 3 students in one Singapore school participated in this study. Findings suggested that while students were motivated to learn in CSCL environments, they had difficulties monitoring and sharing knowledge for their own understanding. Additionally, a great deal of teacher guidance was needed to encourage student participation in collaborative knowledge building processes. Overall, this study may imply that students at this early stage of schooling need more structured guidance to improve their understanding in CSCL environments.