This study aimed to evaluate the in vitro efficacy of the essential oil of Croton pulegiodorus collected from the semi-arid region of Bahia, Brazil, as an alternative control strategy against Rhipicephalus (Boophilus) microplus, as well as to perform its chemical characterization in order to identify and determine the major compounds associated with acaricidal activity. The essential oil of C. pulegiodorus was obtained by hydrodistillation using a Clevenger-type apparatus and chemically characterized by gas chromatography coupled to mass spectrometry (GC–MS) for the identification of major compounds. Eight concentrations of essential oil (0.78, 1.56, 3.12, 6.25, 12.5, 25, 50, and 100 µL), diluted in distilled water, were tested using the Adult Immersion Test (AIT), in which engorged adult females of R. (B.) microplus were immersed in the test solutions for 5 minutes, dried, and kept under controlled conditions for the evaluation of reproductive parameters. Statistical analysis was performed by analysis of variance (ANOVA), followed by Tukey’s test at a 5% significance level. GC–MS analysis of the essential oil of C. pulegiodorus revealed a complex chemical composition predominant ly composed of mono- and sesquiterpenes. The major constituents identified were p-cymene, a-terpinene, ?-terpinene, 1,8-cineole, a-terpineol, ß-caryophyllene, humulene, caryophyllene oxide, spathulenol, t-cadinol, and isoaromadendrene epoxide.In the AIT, the essential oil exhibited a concentration-dependent effect against R. (B.) microplus, with oviposition inhibition rates of 6, 16, 6, 27, 28, 61, 100, and 95% and corresponding treatment efficacies of 13, 28, 19, 40, 42, 75, 100, and 97%, respectively. One-way ANOVA revealed significant differences among treatments (p < 0.05). Dunnett’s post hoc test indicated that concentrations of 1.56 µL (p = 0.0180) and = 6.25 µL (p = 0.0003) differed significantly from the control, whereas 0.78 and 3.12 µL did not show significant differences (p > 0.05). The highest concentrations (50 and 100 µL) achieved 100% and 97% treatment efficacy (p < 0.0001), respectively. These results demonstrate the strong acaricidal potential of C. pulegiodorus essential oil as a promising alternative strategy for the control of the tick R. (B.) microplus.