The present study aimed to evaluate the activity of Lippia gracilis Schauer essential oil obtained from different L. gracilis genotypes and their major components, carvacrol and thymol against Rhipicephalus (Boophilus) microplus (cattle tick) larvae and engorged females. The larval test was performed parallel to the adult immersion test for engorged females for four L. gracilis genotypes. Similar tests were further performed for their major compounds carvacrol and thymol. Carvacrol (LC(50) of 0.22 and 4.46mg/mL, to larvae and engorged females, respectively) was more efficient than thymol (LC(50) of 3.86 and 5.50mg/mL, to larvae and engorged females, respectively). The lethal concentrations obtained for the isolated essential oil from genotypes LGRA-201 against larvae (1.31mg/mL) and LGRA-106 against engorged females (4.66mg/mL) confirmed the acaricidal activity of L. gracilis essential oil and its effectiveness in controlling the southern cattle tick.