Retained placenta is considered to be a problem in postpartum mares. Retained placenta was defined as a failure to expel all fetal membranes within 3 h of the delivery of the foal. The incidence of retained placenta in mares varies from 2% to 15% of foaling. Retained placenta was associated with lower postpartum oxytocin and calcium concentration, uterine inertia, placentitis, histological abnormalities, and dystocia. Complications of retained placenta include acute metritis, endometritis, reduction in fertility, endotoxemia, septicaemia, laminitis, and even death. Treatment options vary from conservative therapy (antibiotic, nonsteroid antiinflamatuar durugs, fluid etc), oxytocin therapy, infusion of fluids into the chorioallantoic space, injection of collagenases into the umbilical arteries, and manual removal of placenta. In this review, causes and treatment of retained placenta in mares were evaluated in the light of recent literature.