Abstract Essential oils are considered an alternative for replacement of conventional insecticides that have provoked an increasing number of resistant species and damages to health. The objective of this work was to investigate the insecticidal activity of Lavandula dentata L. (Lamiales: Lamiaceae) oil against the species Musca domestica L. (Diptera: Muscidae) and Chrysomya albiceps Wiedemann (Diptera: Calliphoridae). Extraction of the essential oil from the aerial parts of the plant was carried out using hydro-distillation. Its principal compounds (1,8-cineol, camphor, and linalool oxide) were identified. Insecticidal activity was determined by evaluating adulticidal effect using topical application methods and exposure to impregnated paper; larvicidal effect was determined using immersion method. The essential oil presented toxicity in M. domestica and C. albiceps adults; the lethal concentration values (LC50) in the superficial application method were respectively 3.13 ± 0.64 and 1.39 ± 0.19% live weight (l/v). Toxicity was also found in the oil impregnated paper exposure test; the LC50 results for M. domestica and C. albiceps were respectively 4.15 ± 0.64 and 5.14 ± 0.81%. Larvicidal effect was observed on third stage M. domestica larvae when exposed to an oil concentration of 2.5% (m/v). In addition, the oil was evaluated for cytotoxicity, mutagenicity, and genotoxicity in human cells, and the in vitro safety of this oil in human cells was verified. Thus, L. dentata oil presented insecticidal activity in M. domestica and C. albiceps and can be used as an alternative for control of these dipterans.