Background: Helminthiases inflict annual losses on the meat and dairy livestock industries. The commonest species of ruminant parasites are the nematodes: Strongyloides papillosus and Haemonchus contortus, which lay eggs in the intestine and enter the feces. There, the eggs develop into larvae, which when voided with the feces crawl onto plants. Methods: In our experiment, we evaluated the survivability of the noninvasive and invasive (L{}_{1-2} and L{}_3, respectively) larvae of S. papillosus, H. contortus (L{}_3), and Muellerius capillaris (L{}_1) in vitro by subjecting each to natural compounds present in the essential oils of many plants. In the experiment, we used aqueous emulsions of eugenol, isoeugenol, thymol, and carvacrol. Results: Administering 1% concentrations of those compounds killed 100% of the nematode larvae following 24 h of exposure. Thymol, eugenol, and isoeugenol at a concentration of 0.1% also caused high larvae mortality (over 96%). Conclusions: Continuous usage of synthetic anthelmintic drugs in veterinary medicine has led to the parasites developing resistance, thus, a search for novel nematicidal drugs is required. Eugenol, isoeugenol, thymol, and carvacrol are promising compounds against nematodes. However, additional research is required regarding peculiarities in their actions toward the bodies of mammals and parasitic nematodes.