This study examined peer social support, locus of control as determinants of school adjustment among freshmen in Nasarawa State University, Keffi, Nigeria. The study adopted Ex post facto as research design. The sample comprised 600 participants randomly selected from all the schools/faculties (as used in Nigeria). A total of 75 students were each randomly selected from each of the eight schools/faculties (as used in Nigeria) of the university. Three research instruments were used to collect data for the study, these are: the student adjustment to university questionnaire by Baker and Siryk (2004), the locus of control scale by Hunttley, Palmer and Wakeling (2011), and the peer support scale by Kamalevva (2006). The results revealed that peer social support (emotional, instrumental, informational and appraisal supports) predicted school adjustment. Also, internal locus of control positively predicted school adjustment of university freshmen; in contrast to external locus of control. Significant difference exists in school adjustment of students with internal and external locus of control. Based on the findings, it was recommended among others that Nigerian universities should organize social forums that will afford fresh students opportunities to interact and receive support from their peers, as well enhancing their internal locus of control.