In addition to a phytochemical screening of the essential oil of Ruta chalpensis aerial parts, this study aimed to discover its eco-friendly acaricidal activity against the cattle tick Rhipicephalus annulatus (Acari: Ixodidae). The essential oil obtained by hydro-distillation from fresh R. chalepensis aerial parts was analyzed by gas chromatography-mass spectrometry. Acaricidal activity was evaluated against Rhipicephalus annulatus ticks by using an adult immersion test. A total of 33 compounds were identified that represented 99.58% of the oil composition. The main constituents of the oils were 2-Nonanone (27.76%), 2-Undecanone (27.12%), 2-Heptyl acetate (10.79%), 2-Acetoxytridecane (4.24%), 5,6-diethenyl-1-methyl-Cyclohexene (3.31%), Davanone (2.87%) and 2-Decanone (2.41%). The results revealed the presence of a high percentage of the two main classes ketones (64.33%) and Esters (19.93%) with a low quantity of various terpenoid classes. The essential oil revealed strong acaricidal activity against semi-engorged females of R. annulatus ticks recording LC₅₀: 1.9% and LC₉₀: 10.3% on the 1^st day post-treatment.