Aim: To present an uncommon case of allantoic duct cyst of the umbilical cord (UC), detected incidentally during the histopathological evaluation of the placenta sent for evaluation of suspected chorioamnionitis in a case of antenatal care (ANC) with post datism and leaking P/V with meconium-stained liquor, who underwent emergency lower segment cesarean section (LSCS) and had an uneventful fetal outcome. Background: Allantoic duct cysts of the UC are the embryological remnants of either the allantois or the omphalomesenteric duct and represent true cysts of the UC. They are uncommon and have a reported incidence of less than 1%. Most often, they are associated with additional fetal abnormalities and unfavorable fetal outcome. Isolated UC cysts resulting in an uneventful fetal outcome are rare. We present one such case of an incidentally detected UC cyst with no associated fetal abnormalities resulting in a favorable outcome. Case description: Allantoic duct cyst of UC detected incidentally during the histopathological evaluation of the placenta sent for evaluation of suspected chorioamnionitis in a 24-year-old case of ANC with post datism and leaking P/V with meconium-stained liquor, who underwent emergency LSCS and had an uneventful fetal outcome. Conclusion: Embryonic remnants of the UC, when persistent, may present as UC cysts, which can be diagnosed during pregnancy with careful routine ultrasonography examination. Most UC cysts are associated with fetal anomalies, and it is uncommon to have an isolated UC cyst with a normal fetal outcome. Clinical significance: UC cysts, when noted, always necessitate a complete postnatal clinical and histopathological examination of the neonate as well as the placenta along with karyotyping to rule out the presence of structural and/or chromosomal abnormalities associated with these cysts. This case has been reported to increase the awareness as well as the number of cases of true UC cysts in literature, and to promote research regarding the association of such cysts with placental abnormalities, including chronic placental insufficiency.