Objective To assess the prevalence of sexual activity and family-planning use among undergraduates in a private tertiary institution in Nigeria.Methods A cross-sectional survey of 283 undergraduate students.Results Out of 283 students, 245 (86.6%) are sexually active in the last month. Out of these 245, 219 (89%) are currently using a family-planning method. In the study population, the percentages of awareness, ever use, and current users are 89%, 77%, and 75%, respectively. The most commonly known, ever used, and currently used contraceptive is condom followed in descending order by calendar method, oral pills, coitus interruptus, injectable contraception, emergency contraception, intrauterine contraceptive device, and diaphragm. Unmarried students and male gender show statistical significance with condom use. The reasons for preferring the current contraceptive method, among 219 current users, include safety, cost, ready availability, and partner's preference, among others. Most of the nonusers gave no reason for a failure to use a contraceptive, but others felt that contraceptives are dangerous, while a minority were ignorant of any method. Though many use a condom, this use is inconsistent.Conclusion There is a high level of sexual activity among these undergraduates. Many are aware of family planning, and the condom is the most commonly known and used method, though not consistently. Reproductive-health education should be promoted among youths in Nigeria.