Our study investigated the effects of extracts from tobacco (Nicotiana rustica L.) and stemona (Stemona tuberosa Lour.) on parasitic ticks infested on dogs, in order to give a pharmacological explanation for their traditional uses in ectoparasite diseases. The comparison of extracts from different solvents with different extracting times revealed that NaOH 5% with water was the best extracting solvent, while 24 h was the best extracting time for the extraction of these plants’ acaricidal effects. After applying these optimal solvent and extracting time to yield those extracts of the highest effects, we examined their effects on ticks at different concentrations, and the results showed that they exerted their best effects when being applied at 20%. These effects were later confirmed by clinical trials, which demonstrated that the extracts also had high treatment effects on those dogs that had been heavily affected with tick diseases. These results partly provide scientific explanations for the therapeutic uses of tobacco and stemona in ectoparasite diseases. In addition, the promissory treatment observed in clinical trials is a step forwards to widen the uses of these medicinal plants in tick diseases, and thus suggesting that follow-up researches are worth to exploit their potentials