The purpose of this study is to investigate the influence of peer group on adolescent and their academic performance. Descriptive research methodology was used. Random sampling techniques was also adopted to select about one hundred in schools adolescents from four secondary schools in Egor Local Government Area of Edo State. Questionnaires were developed to collect data. The data collected was analyzed using the t-test and parson. The findings of this study revealed that peer group could either positively or negatively influence the academic performance of in school adolescents. This research recommends that parents and teachers should provides adequate guidance to adolescents to help them understand how the friends they keep can either positively or negatively influence their academic performance in school.