This paper reports on the effects of two different dynamic grouping strategies in a mobile-assisted Chinese character learning game. The game application assigns each student a component of a Chinese character through their smartphones and requires them to form groups that can assemble a legitimate Chinese character using the components held by the group members. Sixteen Primary 3 (3 rd grade) students taking Chinese as a second language (L2) class involved in the study. Video-recordings of the game and the transcriptions of focus group interviews were qualitatively analyzed. The study aims to explore the patterns of social interactions during the game, especially on the varied impacts of the two different grouping rules (allowing versus not allowing each student to join more than one group at one time) on the student game behaviors and their learning gains.