Effect of three different anti-helminthic drugs  (ivermectin, levamisole and albendazole) on quality and fertility of spermatozoa of frozen-thawed semen of Frisian bulls .Animals were divided into four groups, control untreated group, and bulls treated with 200 µg/kg of ivermectin (IVM), 7.5 mg/kg of levamisole (LEV), and 10 mg/kg of albendazole (ABZ),  respectively. The drugs used at two doses with 8-week interval between first and second dose. Semen was collected for 8^th weeks after each dose, extended, and frozen for two months, then post-thawing motility, freezability, intact acrosome and DNA integrity were determined. After the second dose, bulls treated with IVM and LEV significantly (P<0.05) increased post-thawing motility, freezability and intact acrosome. Bulls treated with IVM did not negatively influenced DNA integrity, while LEV treatment affected negatively on DNA integrity by increasing tail moment percentage. Either first or second doses of ABZ did not negatively affect post-thawing motility, freezability, intact acrosome and DNA integrity. Fertility rates of the cows artificially inseminated with the frozen-thawed semen were significantly (P<0.05) higher when they were inseminated with semen of bulls treated with IVM or LEV and untreated bulls (control) than those treated with ABZ. In conclusion, treatment of Friesian bulls with Ivermectin as anti-helminthic drug at a level of 200 µg/kg live body weight improved post-thawing motility and freezability of spermatozoa, percentage of spermatozoa with intact acrosome, and maintained DNA integrity and subsequent fertilizing efficiency of bull spermatozoa as compared to control bulls or bulls treated with Levamisole (7.5 mg/kg) or Albendazole (10 mg/kg) either after the first or second dose.