The aim of this research was to evaluate an ethanolic extract from Enterolobium cyclocarpum leaves against infective larvae of Haemonchus contortus, considered one of the most pathogenic gastrointestinal nematodes due to its haematophagous habits and its high prevalence and pathogenicity in small ruminants. The study was carried out at the Faculty of Agricultural and Environmental Sciences of the Autonomous University of Guerrero. Infective larvae were obtained by culturing feces from a donor sheep using the Baermann technique. The percentage mortality test, 96-well microtiter plates were used with the following treatments: 25, 12.5, 6.25 and 3.12 mg/mL, and a positive control (ivermectin 0.5%) and negative controls (distilled water and 4% methanol) in triplicate generating 12 experimental units, distributed in a completely randomized design and analyzed by PROBIT and ANOVA. The results revealed that the highest percentage of mortality was 93.97 ± 2.52 at a concentration of 25 mg/mL, while 3.12 mg/mL exhibited 68.25 ± 1.13 mortality at 72 hours post confrontation. On the other hand, the 220 lethal concentrations of the ethanolic extract after 72 h of exposure to cause 50 and 90% mortality were at 3.17 and 41.24 mg/mL respectively. The use of this tree legume represents an alternative use for the control of nematodiasis in small ruminants, because the leaves of E. cyclocarpum contain secondary metabolites responsible for the larvicidal activity.