Sexual development of the youth has increased in the society and public health concerns of all involved. This study investigated the influence of peer pressure on sexual behavior of undergraduates in Kwara State. Descriptive research design was adopted for the study as well as multi stage sampling procedure. A total of 395 undergraduates participated in the study, four research questions were generated to guide the conduct of the study, while three null hypotheses were formulated and tested at 0.05 level of significance. The instrument used for data collection for this study was a researchers-designed and structured questionnaire entitled "Influence of Peer Pressure Questionnaire" (IPPQ). The findings revealed that the influence of peer pressure on sexual behavior of undergraduates reveals that it leads students to erotic electro-stimulation, prostitution, risk of contracting Sexually Transmitted Diseases (STD) and involvement in incest. There were no significant differences in the influence of peer pressure on sexual behavior of undergraduates in Kwara State based on gender and age. There was a significant difference in the influence of peer pressure on sexual behavior of undergraduates in Kwara State based on university attended. It was therefore recommended, among others that counsellors should enlighten the students on how peer pressure could be used to channel the students' behavior towards positive activities, counsellors should inform the students about the positive and negative influence of peer pressure to enhance self-esteem and social skills rather than for abusive purposes to students of different gender and age and counsellors should look for underlying issues that may have led to exhibition of risk sexual behavior through peer pressure and try to identify the perpetrators so that the victims could be offered counselling on assertiveness skills, socialization skills and improving self-concept.