Recent findings indicated that plant-based diet minimizes the overall cancer risk. Accordingly, there is a great concern with the therapeutic and anticancer uses of plant essential oils. The current work aimed to evaluate the protective activity of Eucalyptus globulus essential oil (EGEO) against genotoxic and histopathological defects induced by mitomycin C (MMC) in mice. Sixty male mice were subdivided into six groups: I: Control negative; II: Treated with 1.2 mL EGEO/kg for 4 days; III: MMC (1.5 mg/kg); IV-VI: three combined groups treated with EGEO at (0.8, 1.0 or1.2 mL/kg) plus MMC at (1.5 mg/kg). Twenty-one compounds, with the superiority of eucalyptol (74.31%), were determined in EGEO using Gas chromatography–mass spectrometry (GC/MS) analysis. Treatment with MMC triggered substantial genotoxic and histopathological lesions in mouse tissues. MMC induced defects were significantly reversed by EGEO treatment at the tested doses. Chromosomal aberrations (Cas), micro-nucleated polychromatic erythrocytes (MNPCEs), comet tail formation, inflammatory cell infiltration, necrosis, Kupffer cells, and pyknotic cells were all relevantly diminished. In conclusion, EGEO could be a safe and promising candidate for pharmaceutical and food industries. The synergistic effects of EGEO active constituents could alleviate the chemotherapeutic agents MMC-induced genetic and histological defects, thereby improving biological activities.