This study surveyed the influence of peer group on academic performance of undergraduate students in selected departments in Babcock University, Ogun State. Peer group plays a large role in the social, emotional and academic development of students; therefore, understanding the prospects and challenges of peer group is crucial for the productivity of educational processes and the organizational design of school systems in order to improve student's academic performance. The study adopted mixed method design incorporating descriptive survey and ex post facto designs. Questionnaire was administered to one hundred and sixteen (116) students drawn from five (5) departments in the School of Education and Humanities. The number was derived from the totality of 300 level students of each department of the School using stratified random sampling method. The data generated from the study were analyzed using Pearson Product Moment Correlation Coefficient and Linear Regression Analysis to test the null hypotheses at 0.05 significant level. The result of this study revealed that, peer group has significant influence on academic performance of undergraduate students. Also, there is significant relationship between peer group and academic performance of students. Sequel to these findings, the researcher therefore recommended that, there is need for teacher to have greater supervision and regulations on students while they are in school, this will enhance the type of group they belong to. The government and ministry of education in all levels should ensure that trained counselors are posted in all schools and colleges so as to provide preventive counseling services and modify the behaviors of students who perchance have been negatively influenced by peers. Also, School counselors should play a prominent and leading role in the matter of peer group influence by organizing lectures, seminars, career talk and symposiums that can create positive awareness on influence of peer group on academic performance of undergraduate students.