This case study examined an authentic online learning phenomenon where social conflict, including harsh critique and negative tone, weaved throughout peer-moderated online discussions in an online class. Opening coding and content analysis were performed on 1306 message units and course artifacts. The results revealed that a model of social conflict evolution, that is, social conflict within the learning community evolved through five general phases including cultural initiation, social harmonization cycle, escalation of conflict, intervention and stabilization, and adjourning. The results also suggested strong relationships between social and learning interactions during these five phases of social conflict development. This study has theoretical and practical implications for designing and managing learning activities in online classes. (Contains 2 figures and 4 tables.)