Control methods used to limit field losses caused by Bruchus rufimanus Boheman, 1833 consist of synthetic insecticides that pose health risks to farmers, consumers and the environment. In an attempt to find safer alternatives, we screened essential oils from the leaves of Rosmarinus officinalis collected in the Middle Atlas and Loukkos regions of Morocco in the laboratory as natural fumigants against B. rufimanus. These essential oils were extracted by steam distillation using a Clevenger distiller, characterised chemically by coupled gas chromatography–mass spectrometry (GC/MS) and tested at five concentrations (0, 10, 20, 40, 80 µl/l air). The essential oils of R. officinalis mainly comprised oxygenated monoterpenes (Middle Atlas: 79.4%; Loukkos: 48.78%) and terpenes (Middle Atlas: 14.71%; Loukkos: 32.33%). The lethal concentrations (LC50) of Middle Atlas and Loukkos essential oils against male beetles ranged from, respectively, 46.53 to 1.19 µl/l air and 58.85 to 11.57 µl/l air. Similarly, doses of R. officinalis essential oils from Middle Atlas and Loukkos lethal to females, ranged from 44.6 to 2.08 µl/l air and from 53.00 to 5.38 µl/l air, respectively. Additionally, the lethal time (LT50 and LT99) of exposed adults ranged from 1–8 and from 2–13 days for different concentrations of R. officinalis essential oils from Middle Atlas and Loukkos, respectively. With no mortality recorded in the control groups, these findings demonstrate the fumigant potential of these oils against this bruchid under the storage conditions.