Second language (L2) scholars agreed that L2 gesture is not separable from second language acquisition (SLA) and developed various perspectives on the functions of gesture, but little research has been done to synthesize theoretical approaches with a big-picture view. Hence, this paper summarized these diverse perspectives into two main categories (i.e., psycholinguistics and sociolinguistics), and compared limitations and contributions of each perspective from a critical point of view. In contrast to psycholinguists who focus extremely on the function of gesture for effective communication, socio-cultural scholars consider both social and cognitive functions within the Vygotskyan theoretical framework, whereby cognition occurs first at the interpersonal level and then, the intrapersonal level. Although the intrapersonal perspective has been explored from more balanced viewpoints, neither of the two perspectives has fully examined how L2 gesture functions in SLA yet because of the lack of studies. Therefore, this study provides suggestions for further studies in order to lead L2 scholars to perform theoretically/methodologically well-designed gesture study in the future. Eventually, these guidelines will be conductive to putting forward L2 gesture as a central issue in the field of SLA and suggest how gesture can be utilized for L2 learning and teaching.