The present work evaluates the effect of aqueous and methanolic extracts of Dendrosicyos socotrana and Jatropha unicostata on the viability of Echinococcus granulosus protoscoleces in vitro, and on the development of secondary hydatid cysts, in vivo. Three different concentrations of each leaf extract were used. Concentrations of 5000 and 1000 μg/mL, for D. socotrana and J. unicostata, respectively, exhibited the highest protoscolicidal activity, significantly reducing and/or stopping protoscolex viability. Oral and intraperitoneal administration of the extracts in white mice invoked noticeable inhibitory effects on the in vivo development of secondary hydatid cysts. These effects were compared with those of albendazole sulfoxide, a commonly used treatment for hydatidosis.