Cold storage of stallion semen alters semen characteristics and exposes spermatozoa to oxidative stress. The current study aimed to evaluate the roles of quercetin supplementation in skim milk extender in improving semen quality and preventing lipid peroxidation. Semen was collected from three proven fertile Arabian stallions over 8 weeks using a Missouri artificial vagina. Collected ejaculates were extended with skim milk extender (Kenney extender) supplemented with quercetin at 0 (control), 25 μM, 50 μM, and 100 μM concentrations and cooled to 4 ºC. Cold-stored extended semen was evaluated at 12-hours intervals for up to 72 hours for sperm progressive motility, livability, and total abnormalities. Sperm-free extender samples were assessed for acid phosphatase (ACP), alkaline phosphatase, aspartate aminotransferase (AST), lactate dehydrogenase, Catalase (CAT), superoxide dismutase and glutathione peroxidase, Malondialdehyde (MDA) and acrosin activity. The results showed that quercetin had a significant effect on stallion sperm progressive motility and livability (improved at 60 and 72 hours, respectively), ACP and MDA (reduced at 12 hours), AST (reduced at 24 hours), acrosin (reduced at 1-3 days) and CAT (increased at 1-3 days) during cold storage. The effect of quercetin was prominent at a concentration of 50 μM. In conclusion, quercetin supplementation to the cooled stallion semen extender is beneficial in maintaining progressive motility and livability, lower extra-cellular escape of enzymes and decreasing lipid peroxidation perhaps accused to enhancement of catalase enzyme activity during short term-storage.