Although a great deal of research has evidenced the effects of proper instructional design on multimedia learning, most has focused on the cognitive aspects of learning, with little concern about the role of affective-motivational states in multimedia learning. In this study, an AR game-based learning method was designed via integrating AR technology and a digital game for assisting students' learning, and for probing the factors of metacognitive and motivational factors of multimedia learning. A context-aware mobile learning system with reflection prompts was developed based on the implemented approach. Furthermore, a 2 × 2 experiment was conducted to identify the impacts of the implemented approach on elementary school science learning. Four groups learned with different media mechanisms (i.e., AR or Non-AR) and gaming mechanisms (i.e., Game or Non-game) during an elementary school field trip. The research results displayed that interaction between the AR and game approaches did not exist, and both significantly promoted the students' learning motivation; however, only the game approach significantly improved the students' learning achievements and flow states. This study evidenced the significance of flow state in a reflective context in multimedia learning. Such a result also stresses that digital games play an important role in promoting affective-motivational states in multimedia learning.