The promise of using games for learning is that play- and learning-engagement would occur cohesively as a whole to compose a highly motivated learning experience. Yet the conceptualization of such an integrative process in the development of play-based learning engagement is lacking. In this analytical paper, we explored and conceptualized the nature and development of game-based learning engagement via an iterative, two-stage analytical process. The first stage was theory driven. The literatures on motives of play, game and cognitive engagement, and game-based learning were reviewed and analyzed. Theoretical discussions on how learning engagement is activated and sustained during gameplay were distilled. The second stage was data driven. An in situ, multiple-case study was conducted to further examine affective and cognitive facets of learning engagement in gaming. The finding suggested that game-based learning engagement is an integrated and continuing process that advances from affective engagement driven by optimal challenge, cognitive engagement situated in playfulness, to potentially game-action-based content engagement.