<p>Knowledge Building (KB) is an educational approach that aims to foster communities of students to identify, solve and refine their knowledge of a subject. This study explores the relationships between university students' epistemic emotions and their achievement in Knowledge Building discourse and, examines whether engaging in reflective assessment can enhance these emotions and achievements. This quasi-experimental study aims to analyze the effects of reflective assessment in an educational research course with 113 students new to KB. Students' epistemic emotions were collected using self-reported surveys, while data about the quality of contributions were collected using Knowledge Forum (KF) platform. Our results show the relationship between epistemic emotions and quality of discourse. In addition, results indicate that reflective assessment contributes to positive emotions and the quality of discourse on the educational online platform KF. This study suggests that reflective assessment enhances the quality of KB discourse and shared knowledge, even when students are unfamiliar with KB pedagogy.</p>