In an effort to understand how collaborative teacher interaction is contingent upon teacher characteristics and school-organizational contexts, this study conducts a series of hierarchical generalized linear modeling analyses based on a nationally representative sample of about 2,500 teachers across 149 middle schools in South Korea. The data are from the OECD Teaching and Learning International Survey 2008. The result from this study suggests that teacher collegiality may be understood largely as teachers' collective effort to deal with uncertainties that arise from their approach to teaching as a constructivist endeavor to engage students in meaningful inquiry-based learning. This result is very robust as it holds after a range of other factors such as principal instructional leadership and teacher efficacy are simultaneously taken into account.