This study aimed to evaluate the spermotoxic potential of triazophos in rats and to check the possible shielding effect of quercetin and nano-quercetin against triazophos-induced toxicity. Rats in Group I were given olive oil as a vehicle. Group II and Group III received high-dose and low-dose triazophos, respectively. Oral administration of quercetin (Group IV) and nano-quercetin (Group VI) at a dose of 50 mg/kg body weight was given to two additional groups of animals. Two other high-dose triazophos groups were co-administered with quercetin (Group V) and nano-quercetin (Group VII).Triazophos administration for 60 days in rats altered the structural and functional parameters of spermatozoa and brought about a decline in total sperm count, percentage of viable sperms, drop in sperm motility, and decrease in the number of sperms showing normal morphology. It also decreased the number of spermatozoa with intact acrosomes and HOST-positive spermatozoa. Further, triazophos increased the levels of reactive oxygen species and triggered apoptotic pathways in spermatozoa in a dose-dependent manner. It decreased daily sperm production and caused histomorphological aberrations in the epididymis and vas deferens. Co-administration of nano-quercetin with triazophos effectively counteracted sperm-related pathological changes. Nano-quercetin offered better protection over quercetin in ameliorating the triazophos-induced spermotoxicity in rats.