Endometrial cyst is a fluid filled structure originating from the uterine wall of old mares and may complicate the pregnancy diagnosis. This study evaluated the outcome of diode laser ablation of endometrial cysts under the guidance of hysteroscopy. Sixteen infertile Straight Egyptian Arabian mares (9-22 year) with a history of normal cycling and infertility over the last two years and diagnosed with endometrial cysts were enrolled in the study. Trans-rectal ultrasonography, hysteroscopy and laser ablation were performed in all mares. The uterine wall had 1-8 endometrial cysts that were mostly located at the uterine body and at the base of uterine horns. Ultrasonographically, endometrial cysts were visualized as anechoic, mostly rounded, structure with thin echogenic wall of 3-8 cm diameter. Mares were divided into two main groups (n=8 mares) according to breeding management. Group 1 (G1) was intended for embryo transfer while group 2 (G2) was intended for normal pregnancy. Embryo recovery rate in G1 and conception rate in G2 were recorded. The embryo recovery rate was 62.5% in G1 and the conception rate was 75% in G2. In conclusion, laser ablation of endometrial cysts is recommended for infertile mares with endometrial cysts for improvement of fertility. Laser ablation is easy, safe and successful treatment for endometrial cysts in mares.