Epidemiologically Haemonchus contortus is the most important parasite in the tropics, females can produce up to ten thousand eggs and blood feed. As objective, it was evaluated the in vitro effect of the secondary compounds of Guazuma ulmifolia leaves extracted with hydroalcoholic (HA) solvent and by fractionation in liquid-liquid layer with ethyl acetate, to inhibit eggs hatching of H. contortus, to interrupt the biological cycle of the parasite. The bioactive compounds were identified by high performance liquid chromatography. Challenged doses were in the HA extract 1.25-40mg/mL, and aqueous and organic fractions of 1.25-10 mg/mL, respectively, distilled water and 2% methanol were negative controls and thiabendazole (0.1 mg/mL) positive control, for a total of seventeen treatments. The treatments were tested in three replicates with four repetitions, the data were analyzed with a GLM in a completely randomized design using ANOVA to an alpha ≤0.05. The effective concentrations (EC₅₀ and EC₉₀) were estimated by Probit analysis in the SAS program. The secondary compounds identified were of the phenols group such as flavonols, flavones, coumaroyl derivatives and hydroxycinnamic acid. The HA extract and aqueous fraction showed a similar effect to the positive control from doses of 2.5 mg/mL and the organic fraction from 1.5 mg/mL (P<0.01). In HA extract and aqueous fraction, the EC₅₀ and EC₉₀ were similar, but in the organic fraction the ovicidal effect was at lower EC₅₀ (0.86 mg/mL) and EC₉₀ (1.67mg/mL). In conclusion G. ulmifolia leaves contain secondary compounds able for interrupting the cycle of H. contortus in the egg stage and the content of phenols like hydroxycinnamic acid and coumaroyl derivatives could be responsible for the ovicidal effect.