In this article, ethanol sclerotherapy was proposed for the treatment of large uterine cysts in the mare. Eight infertile mares, aged between 13 and 21 years, with large uterine cysts and without other detectable causes of infertility were selected. The cysts were emptied endoscopically, and 70% ethanol in saline solution was injected to fill 40% of the original volume. The mares were monitored clinically and ultrasonographically at 4 hours and at days 1, 3, and 14 after the treatment, as in the following estrus cycles. The cysts, which at diagnosis ranged between 4 and 6 cm in diameter, were between 0 and 0.5 cm after 4 hours and were not detectable in the following evaluations. No side effects or a recurrence of the uterine cyst were recorded. Fertility was recovered in 87.5% of the treated mares. The ethanol sclerotherapy seemed useful and safe to treat uterine cysts in the mare, also when the cysts were not pedunculated.