Leiomyomas are the most common of uterine tumours in mares but large tumours are rare. A case with a 15 cm uterine leiomyoma diagnosed by rectal palpation and ultrasound examinations with apparent adverse effects on fertility is reported. Management of the case was by hand assisted laparoscopic tumour removal and unilateral ovariectomy. Complications included post operative pain, tachycardia and wound infection. The mare was confirmed to be in foal after her first cover post surgery.