This mixed methods study investigated the dynamic impacts of instructor moderations and peer reviews on critical thinking (CT) in a virtual learning community. Multiple data sets were collected from online discourses, participants’ written reflections, and learning artifacts, and analyzed and triangulated with both quantitative and qualitative methods. Both instructor moderations and peer reviews had great impacts on learner’s CT in multiple ways, and stimulated CT development throughout the semester. As learners grew with more CT skills, the needs for instructor moderations decreased; yet peer reviews peaked in terms of quantity, length, and depth of discussions. Peer reviews in this study also demonstrated effective questioning patterns, which were positively accepted by students being questioned or criticized, and resulted in changes and improvements in the final learning artifacts. Practical implications for online teaching and learning and community building are discussed, together with suggestions for future research.