Previous research investigating the relationship between peer-assisted study sessions (also called supplemental instruction or peer-assisted learning) and academic performance has a number of concerns. These include the lack of inclusion of important variables such as academic motivation and personality. This study (N = 233) investigated how motivation, personality, and control variables (prior subject attempts, number of university semesters completed, prior academic achievement) have an impact on the relationship between peer-assisted study sessions attendance and academic performance for psychology students. The results indicated that peer-assisted study sessions attendance predicted academic performance when controlling for academic motivation, personality, and control variables; however, the magnitude of the relationship was almost halved (r = .27 to ß = .13). Peer-assisted study sessions attendance mediated the relationship between neuroticism (κ2 = .04) and prior academic achievement (κ2 = .05) and academic performance, indicating that participants with these characteristics benefit from the sessions. Finally, adjunct peer-assisted study sessions focused on assessment items appear to be a large part of its efficacy in this sample.