Overproduction of reactive oxygen species during sperm freeze-thawing cycles leads to membrane lipid peroxidation, DNA damage, motility loss, and subsequent death. This oxidative stress can be alleviated by the addition of some antioxidants to semen extenders prior freezing. The present study was performed to evaluate the in vitro effectiveness of quercetin on stallion sperm freezability. Ejaculates from healthy Turkmen stallions (n = 4), which exceeded minimum standards, were pooled, and aliquots of each pool were diluted in an egg yolk–based extender added with different concentrations of quercetin (0.1, 0.2, and 0.3 mM) and two control groups (positive: base extender + 0.5% ethanol and negative: base extender). The following parameters were determined: sperm motility and kinematics, viability, morphology, membrane integrity, and lipid peroxidation. Results showed that, except for motility and kinematics in which 0.1 mM quercetin exerted significant improving effects (P < .05), the other parameters investigated were not affected (P > .05). Additionally, higher concentrations of quercetin (0.2 and 0.3 mM) exerted partially prooxidant activity on sperm viability and membrane integrity. Therefore, 0.1 mM of quercetin seems to relatively protect sperm motility during cryopreservation.