This study explored the impact of reflection on learning in an online learning environment. Twenty-five students from four online courses (two courses, each with two sessions) participated in this research project. Reflection was purposefully designed and embedded in various assignments. Data were mainly collected from interviews and students' various types of reflections. The inductive content analysis method was employed to analyze data. Five themes were generalized in terms of how reflection impacts learning: Increasing the depth of knowledge, identifying the areas which are missing or deficient, personalizing and contextualizing knowledge, providing comparative references in learning, and helping learners build structural connections in knowledge and social connections among learners. This study provides foundational ideas for designing reflective activities to promote students' learning in an online learning environment.