Adding quercetin to rooster semen extender improves sperm quality after freezing and thawing. Different concentrations of quercetin were tested, with 0.010 mg/mL showing the best results for sperm motility, membrane function, viability, and enzyme activity. 0.005 mg/mL also improved sperm quality, while 0.020 mg/mL reduced DNA damage. Overall, quercetin supplementation decreased abnormal sperm and oxidative stress, enhancing post-thaw semen quality.