This study examined the promiscuous behaviour of female undergraduate students and the various health issues related to it. It also investigated the relationship between the University lifestyles and female students’ promiscuous behaviour. The study adopted descriptive survey with a sample of one hundred and twenty (120) undergraduate female students selected using simple random sampling technique. A questionnaire titled “Sexual Promiscuity (SP) designed by the researcher was used to collect data for the study. Two hypotheses were formulated to guide the result of the study. The study revealed that there was a significant relationship between the female undergraduates’ promiscuous behaviour and their University lifestyles X2= 178.092<0.05). Also, there was significant relationship between the promiscuous behaviour and sexually transmitted diseases (X2 = 70.69<0.05). It was therefore concluded that female undergraduate students of Adekunle Ajasin University were promiscuous because of their University lifestyles and that many were exposed to various sexually transmitted diseases that affect their health. Recommendations were based on the findings of the study that the University lifestyles of students should be modernized to discourage promiscuous behaviour among female undergraduate students. Besides, adequate health and counselling seminars should be organized on regular basis to intimate female students with the consequences of such promiscuous lifestyles.