Background: Natural products demonstrated potential for use in medicine and pharmaceuticals. Objective: This study evaluated the phytochemical composition of Urtica sp. leaves extract (USLE), and its in vitro and in vivo antitumor effects. Methods: HepG-2 and MCF-7 cell lines were used to evaluate the IC₅₀, apoptosis, and cell cycle analysis of USLE. Forty female CD-1 mice were equally divided as follows; Gp1 was control; Gp2, Gp3, and Gp4 were inoculated with 1 × 10⁶ of Ehrlich ascitic carcinoma (EAC)-cells/mouse. Then, Gp3 had injected with Cisplatin (2 mg/kg) intraperitoneally (i.p). Gp4 had injected with USLE (100 mg/kg) i.p. as in Gp3. Total tumor volume, total tumor cell count, and live and dead EAC-cells were determined, also biochemical and histopathological investigations were evaluated. Results: Data showed that the USLE had cytotoxic and antitumor effects against the HepG-2, MCF-7, and EAC-bearing mice. Biochemical and histopathological investigations showed an improvement in the liver and kidney tissues upon treatment of EAC-bearing mice with USLE. Conclusion: The results showed that the USLE can stop tumor growth and cause tumor cells to die.