Previous research indicates the importance of student discourse in the construction of knowledge and the fostering of critical thinking skills, especially in the field of problem-based learning (PBL). Further, a growing body of research on game-based learning (GBL) draws parallels between playing certain types of games and the solving of ill-structured problems, citing similar conditions for learning (student centered, small student groups, teachers as facilitators, problems as vehicles for development), and similar learning outcomes (communication, problem-solving, critical thinking, collaboration) as PBL. However, there is a gap in understanding how GBL affects critical thinking as embodied by student discourse when implemented in traditional classroom environments. In this study, I examined student discourse throughout a GBL intervention designed to promote content knowledge and critical thinking in an 8th grade social studies classroom. A total of three 8th grade social studies classes engaged in the intervention. Post-tests and delayed post-tests were conducted for the entire 8th grade (ten social studies classes across two instructors). Five groups of students that engaged in the GBL intervention were videotaped and analyzed. Data analysis showed that features of the GBL intervention and particular cycles of gameplay were effective in promoting higher levels of critical thinking, including the development of independent beliefs prior to engaging in collaborative discourse and providing opportunities for guided reflection. This study has implications for the developers of GBL frameworks, researchers interested in exploring GBL, and teachers seeking to integrate GBL into their classrooms.