Eucalyptus camaldulensis Dehnh (Myrtaceae) is used in traditional folk medicine for the treatment of various health complications are well known. The current study aimed to investigate the antitumor efficacy of Eucalyptus camaldulensis stem bark methanol extract (ECME) against Ehrlich ascites carcinoma (EAC) bearing Swiss albino mice. The extract was proved by chemical analysis and LD50 was determined. Then, mice were injected intraperitoneally with ECME (100mg /kg b.wt) before and after EAC inoculation, to achieve preventive and therapeutic effects daily, for 9 days. Estimating biochemical parameters of experimental mice as malondialdehyde (MDA), total antioxidant capacity (TAC) were estimated, Cytological studies on EAC cells and histopathological examination of liver and kidney tissue were carried out. Treatment with ECME decrease the level of (MDA) associated with increase in (TAC) in preventive and therapeutic groups compared to positive control group. Treatment with ECME reduced most of the pathological alterations induced by EAC cells in mice. This confirmed that ECME caused EAC cell death. The high LD50 value (1120 mg/kg) of ECME indicated its low host toxic effects. The present work indicates that ECME possess significant antitumor and antioxidant activity in vivo. Thus, E. camaldulensis may be considered as a promising resource in cancer chemotherapy.