Plants offer a bountiful source of natural pest control solutions through their essential oils. This research introduces and analyzes an eco-friendly natural essential oil for red flour beetle control. Therefore, the current study was included to show the chemical profile and the insecticidal efficacy of resin essential oil (REO) and its fractions (F_1–3), resulting from chromatographic separation, from the plant Schinus molle against Tribolium castaneum adults. The trunk bark resin essential oil and its fractions’ composition were analyzed by GC-MS. Overall, 33 constituents with 98.3% of the total EO composition were identified. REO and F_1–3 displayed impressive repellent properties at a concentration of 0.12 µL/cm². After 120 min of exposure, repellency ranged from 73.3% to a remarkable 96.7%. They also exhibited noteworthy fumigant properties, with median lethal doses of LD₅₀ = 120.6–160.8 μL/L. The fractions F₁ and F₃ showed the most notable topical toxicity at a concentration of 10%, with LD₅₀ values of 8.6% and 5.6%, respectively. Fractions F₃ and F₂ demonstrated the most effective inhibition of acetylcholinesterase (AChE) activity, providing insight into their insecticidal mechanisms. The in silico molecular docking and DFT studies corroborate the results of in vitro tests performed to identify new insecticide products derived from natural sources.