The authors aimed to extend the literature in self-determination theory (SDT) to understand the relations between college environmental variables (faculty and peer support) and academic major satisfaction. The study was disseminated via an online platform to 320 students attending a large midwestern university. Based on SDT, it was hypothesized that student perceptions of their volitional autonomy, competence, and relatedness in their academic major would fully mediate the relations between perceived faculty and peer supports and major satisfaction. This hypothesized model was tested against a partially mediated model and an alternate model that further tested the directionality of the argument. Results from structural equation modeling partially supported the hypotheses. Faculty and peer support, respectively, significantly contributed to students’ experience of volitional autonomy in their major (βs = .23 and .39), perceived competence in their major (βs = .31 and .37), and relatedness in their major (βs = .29 and .56). Volitional autonomy in a major fully mediated the relationship between faculty support and major satisfaction (M = .14, SE = .05, p < .01, 95% confidence interval CI [.04, .24]) and the relationship between peer support and academic major satisfaction (M = .22, SE = .02, p < .05, 95% CI [.10, .34]). The hypothesized model was found to be superior than the partially mediated and alternate models. Thus, the authors concluded that SDT is a useful framework for understanding the relationship between faculty and peer supports, psychological needs, and major satisfaction.