There is sufficient evidence that suggests Student as Partners' (SaP) practices promote student motivation, engagement, and learning outcomes. This study attempts to understand the underlying mechanism of SaP and its potential to provide the motivational foundation for the students who engage in it and produce quality outcomes. We employ the self-determination theory's (SDT) framework to explain how the processes of partnership lead to students' psychological need satisfaction (autonomy, competence, and relatedness) in order to develop and maintain motivation. The data for this proposition was utilised from the two case studies (Author et al 2018; Author et al., 2017) that were conducted in partnership with students. The three constructs, autonomy, competence, and relatedness served as the framework that guided the data analysis. The findings establish that the social contextual factors posited by SDT for students' need satisfaction fittingly resonate with the principles and practices of SaP. Implications for SaP practitioners are discussed on how SaP can motivate students and sustain engagement