The present article describes studies on the use of veterinary anthelmintic drug “Moxistop” (drops) to prevent helminthiasis in dogs and cats of different ages. These studies are relevant because the market has a wide range of anthelmintic drugs; “Moxistop” with its constituent substances (moxidectin/praziquantel) provides effective prevention of a wide range of helminths. Prevention of helminthiasis is an important anti-epizootic measure, which carried out at least once a quarter. Infection of dogs and cats before and 14 days after treatment was determined by examining fecal samples by Fulleborn flotation. The effectiveness of the drug was established because of the number of helminth eggs in 1 g of feces before and after treatment. For the treatment of dogs was used “Moxistop for dogs” (LLC SPE “SUZIRYA” Kharkiv, Ukraine): the active substances – moxidectin (25 mg/ml) and praziquantel (40 mg/ml), and for the treatment of cats used “Moxistop for cats”: active substances – moxidectin (10 mg/ml) and praziquantel (40 mg/ml). The drug was applied to experimental animals in drops (“spot-on”) on dry intact skin (topical application). As a result of a single application of the drug “Moxistop” drops found that on (4-6) days after application of the drug to dogs and (4-5) days after administration of the drug to cats, diarrhea in all animals stopped, feces became decorated, homogeneous consistency, not had additional inclusions. The animals were not disturbed, did not lick the skin around the anus, no side effects from the skin (redness or irritation, hair loss), increased local temperature or any signs of poisoning. No cat was detected in coprology studies on 14 days after deworming of helminth eggs. In the first series of experiments (groups I and III) conducted on dogs and cats infected with both cestodes and nematodes, a 100% therapeutic effect was obtained in cestodes in dogs and cats. The extent of invasion in dogs with nematodes was 80.0%, and the decrease in the number of eggs after treatment was 97.5% (from 157 ± 13.4 to 4), in cats, these figures were 100%. The effectiveness of the drug “Moxistop” in dogs and cats (groups II and IV animals), which was 100% in the second series of experiments with a high degree of nematode infestation (more than 500 eggs in 1 g of feces). According to the results of the tests, it was found high efficiency of the drug “Moxistop” in the invasion of Dipylidium canis, Toxocara cati, Toxascaris leonina and Uncinaria stenocephala in dogs and cats of different ages