This study evaluated the activity of rosemary (Rosmarinus officinalis) plant extracts on Trypanosomaevansi infection compared to diminazene aceturate drug (DA). Eight extracts wereprepared at concentrations of 4, 10, & 20mg/ml (four from leaves and four from stem bark) ofthe rosemary plant collected from Matrouh Governorate. Petroleum ether, ethyl acetate, ethylalcohol, and distilled water were used in order of increasing polarity. Phytoscreening of thoseextracts and their toxicity were assessed. In vitro & in vivo studies evaluated T. evansi viabilitypost treatment and the efficiency of different extracts. Also, for potential hematological and biochemicalabnormalities that may be associated with the administration of different treatments.The results showed that the phytochemical screening showed significant differences (p≤0.05)between leaves and stem bark components. Extract of 20mg/ml in vitro affected activity of T.evansi more than others but, less than diminazene aceturate without acute toxicity. Statisticalanalysis corroborated anti-trypanosomal activity-specifically correlated to treatment based onsolvent type and plant part extracted. In vivo results showed a significant reduction in infectioninducedalterations in treated groups compared to untreated healthy group. Some extracts didnot achieve complete restoration of some selected biochemical indices to a pre-infection state.