The study investigated determinants of transactional sex among undergraduate students at Ignatius Ajuru University of Education. A descriptive survey research design was used for the study. Two research questions and two hypotheses were stated to guide the study. The population of the study consisted of 15,058 female undergraduate students of Ignatius Ajuru University of Education. A simple random sampling technique was used to select a sample of 450 respondents for the study. A structured questionnaire titled “Determinants of Transactional Sex Questionnaire’’ (DPTSQ) was used for data collection. The reliability coefficient of (DPTSQ) was r=0.82 and was determined using the test-retest method. Mean and standard deviation were used to answer the research questions and independent sample t-tests were used to test the null hypotheses at 0.05 level of significance. The study revealed that poverty and age at sexual debut influenced the practice of transactional sex among undergraduate students at Ignatius Ajuru University of Education. Also, poverty and age at sexual debut significantly influenced the practice of transactional sex among undergraduate students at Ignatius Ajuru University of Education. It was recommended among others that; Nurses who are in charge of school health clinics should counsel undergraduate students on the dangers of transactional sex and also provide them with skills to be able to make the right decisions regarding their sexual lives.