Invertebrates are considered potential sources for drug development. This study was evaluated the biochemical characterization and the in vitro cytotoxic effect of Leiurus quinquestriatus whole-body extract (LQWBE) against HepG-2 and MCF-7 cell lines. For characterization, the total proteins (T.P), lipids (T.L), carbohydrates (T.C), sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE), gas chromatography-mass spectroscopy (GC-MS), and minerals contents were evaluated in LQWB. The results showed that the contents of T.P, T.L, and T.C were 712 ± 8.5 mg/g, 68 ± 3.8 mg/g, and 216 ± 5.2, respectively. SDS-PAGE analysis showed that LQWBE has three bands of 12.5, 20, and 30 kDa. In addition, GC-MS analysis revealed that the presence of 9, 12-Octadecadienoic acid (Z, Z)-, methyl ester at the highest peak area. Sodium, potassium, magnesium, and calcium levels were 9.1 ± 0.16, 35 ± 0.28, 0.2± 0.01, and 5.5 ± 0.77 mg/g extract, respectively. LQWBE showed a mild cytotoxic activity in vitro against HepG-2 and MCF-7 human cancer cells. The LQWBE IC50 against HepG-2 and MCF-7 cell lines were 992 µg/ml ± 49.2 and more than 1000µg/ml after 24 hours of treatment.