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Control measures against common cattle tick <i>Rhipicephalus microplus</i> are of the upmost importance because of considerable, deleterious impact on a farm’s economy. Due to resistance phenomena to synthetic acaricides being a constraint in affected farms, the search for plant derivatives as acaricides has increased dramatically in recent years. In this work, essential oils obtained from two Ecuadorian plants, <i>Ambrosia peruviana</i> and <i>Lepechinia mutica</i> (EO_Ap, EO_Lm), traditionally used as insecticides in indigenous communities, were studied on larvae and engorged females at the parasitic stages of <i>R. microplus</i>. Larvae and females were treated with five (0.0625, 0.125, 0.25, 0.50 and 1%) and six concentrations (0.125, 0.25, 0.50, 1, 2 and 4%), respectively, of each EOs_Ap/Lm. A 98–99% larval mortality was achieved with 0.5% of both EOs_Ap/Lm. EO_Ap inhibited oviposition and egg hatching up to 82% and 80%, respectively, and had an overall efficacy of 93.12%. Efficacy of EO_Lm was 72.84%, due to the low influence of EO_Lm on reproductive parameters. By steam distillation and GC-MS analysis, γ-Curcumene was identified as the main constituent (52.02%) in the EO_Ap and Shyobunol (10.80%) in EO_Lm. The results suggest that major components of both essential oils should be further studied as promissory acaricides against <i>R. microplus</i>.