Based on the tenets of Flow Theory, the study proposes that in-class activities that have the potential to induce the experience of flow--a state of deep absorption and enjoyment of tasks at hand--among students are likely to increase students' engagement. Specifically, the study examined the effects of three in-class activity factors (i.e., optimal challenges, immediate feedback, clear goals) on students' flow experiences and the impact of flow experiences on three classroom engagement behaviors (i.e., silent in-class behaviors, oral in-class behaviors, and thinking about course content). The results of the path analysis conducted on the data collected from N = 213 students revealed that optimal challenges and immediate feedback significantly predicted students' flow experiences. Additionally, students' flow experiences influenced students' engagement behaviors and mediated the relationship between optimal challenges and immediate feedback and the three engagement behaviors. Key findings, teaching implications, and suggestions for future research are discussed.