Congenital adnexum agenesis is a rare finding with a suggested incidence of 1: 11,240. It is usually associated with infertility and rarely seen in pregnancy. Herein, we presented a detailed case report of this rare occurrence of an incidental finding of left adnexum agenesis with their intraoperative images observed at cesarean section in a Nigerian lady at the Kwara State University Teaching Hospital, Ilorin, Kwara State, Nigeria. This finding was observed during an emergency cesarean section carried out on a 23 year old primigravida at a tertiary healthcare facility in north-central Nigeria. Complete agenesis of the left adnexum with grossly normal uterine body and right adnexum (ovary, fallopian tube and broad ligament) was observed. This is a rare condition incidentally found at cesarean section of an otherwise asymptomatic patient thereby throwing more light on its incidence.