One of the success factors in online learning is student engagement. Therefore, the use of technology to influence student engagement in meaningful and effective learning experiences is worthy for investigation. Concept mapping is an effective knowledge construction strategy to help students. This study investigates the influence of concept maps as a formative assessment of online learning and its impact on student engagement and learning outcomes. The design of experiment used the non-equivalent comparison group pretest-posttest. It was included in the quasi-experiment to compare two different groups. The results reveal strong evidence that concept mapping not only improves learning outcomes, but also increases student engagement in all types of tested engagements, namely behavioral, emotional, and cognitive.