Clinopodium rouyanum (Briq.) Govaerts is an endemic species from the mountains of the island of Majorca. In order to assess chemical defense mechanisms of this plant against molluscs, a chemical composition analysis of the essential plant oil (obtained by distillation SDE) and volatiles emitted by green parts, flowers, corollas and tube corollas (obtained by SPME and recent ST methods) – analyzed by GC and GC-MS – was conducted. Additionally, a study on the morphological types and distribution of trichomes was carried out by electron scanning microscopy. Also, the plant’s deterrence to snails was evaluated. The essential oil and volatiles were characterized by a high concentration of oxygenated monoterpenes (83.3–99.9%), whose principal compounds were Pulegone (73.0–93.9%) and Menthone (3.1%–11.8%). Non-glandular tricellular trichomes, peltate trichomes, and capitate trichomes were observed on leaves, calyx, corolla and stems. Volatile components of plants are effective deterrents to a generalist molluscan herbivore and represent an effective defense communication system that favors the conservation of this endangered species.