Amblyomma sculptum is a species of tick in the family Ixodidae, with equids and capybaras among its preferred hosts. In this study, the acaricidal activity of the essential oil (EO) from Piper aduncum and its main component, Dillapiole, were evaluated against larvae of A. sculptum to establish lethal concentration values and assess the effects of these compounds on tick enzymes. Dillapiole exhibited slightly greater activity (LC50 = 3.38 mg/mL; 95% CI = 3.24 to 3.54) than P. aduncum EO (LC50 = 3.49 mg/mL; 95% CI = 3.36 to 3.62) against ticks. The activities of α-esterase (α-EST), β-esterase (β-EST), and glutathione-S-transferase (GST) enzymes in A. sculptum larvae treated with Dillapiole showed a significant increase compared to the control at all concentrations (LC5, LC25, LC50 and LC75), similar results were obtained with P. aduncum EO, except for α-EST, which did not differ from the control at the highest concentration (LC75). The results of the acetylcholinesterase (AChE) activity show an increase in enzyme activity at the two lower concentrations (LC5 and LC25) and a reduction in activity at the two higher, lethal concentrations (LC50 and LC75) compared to the control. These results suggest potential mechanisms of action for these natural acaricides and can provide guidance for the future development of potential plant-derived formulations.