The aim of this research was to study the construct of "engagement," to identify its role in recreation behavior, to empirically validate its influence on the relationship between recreation involvement and flow experience, and to explore the plausibility of promising mediating mechanisms for this construct. We collected 404 questionnaires from hikers in a middle-high altitude mountainous area, and employed structural equation modeling (SEM) to construct the correlations between variables. The results showed that for people participating in hiking activities, those with a significantly greater degree of involvement showed greater engagement. Hikers who showed a higher engagement generally had a greater flow experience. Furthermore, in the relationship between recreation involvement and flow experience, the role of engagement is crucial. In other words, recreation involvement affects flow experience via mediation by engagement. Finally, this study provides suggestions for management and for future research.