Objective: To assess the anti-tumor effects of Pistacia atlantica methanolic extract (PAME) compared with cyclophosphamide against Ehrlich solid tumors in mice. Methods: Swiss albino mice (n=40) were divided into five groups: normal control mice, mice with Ehrlich solid tumors treated with normal saline, mice with Ehrlich solid tumors treated with cyclophosphamide intraperitoneally once a day for 14 d, or 50 mg/kg or 100 mg/kg PAME orally once a day for 14 d. Tumor growth inhibition, body weight, tumor markers, liver and kidney enzymes, oxidative stress markers, antioxidant enzymes, tumor necrosis factor-alpha level (TNF-α), and apoptosis-regulatory gene expression were evaluated. Results: Treatment of mice bearing Ehrlich solid tumors with PAME at 50 and 100 mg/kg orally significantly decreased tumor volume, body weight, tumor markers, liver and kidney enzymes, oxidative stress markers and TNF-α level in comparison with mice with Ehrlich solid tumors receiving normal saline. whereas PAME at 50 and 100 mg/kg/day significantly elevated the level of antioxidant enzymes (P<0.05). Conclusions: Pistacia atlantica methanolic extract has potent antitumor activity in mice. Therefore, the extract might be considered as an alternative anticancer agent against tumors, however, additional studies especially in the clinical setting are required to confirm this finding.