The chemical composition of the essential oil from aerial parts of Calamintha nepeta (L.) Savi, collected in the Campania Region, was obtained by hydrodistillation and analyzed by GC and GC-MS. In all, 42 compounds were identified. The oil was characterized by a prevalence of the sesquiterpenic fraction (80.8%). The main components were 1,10-di-epi-cubenol (18.5%), allo-aromadendrene epoxide (11.4%) and cadalene (5.7%). The essential oil was evaluated for its in vitro potential phytotoxic activity against germination and initial radical growth of Raphanus sativus L., Lepidium sativum L., Sinapis arvensis L., Triticum durum L. and Phalaris canariensis L. seeds. The essential oil showed no antioxidant activity.