Objective: The main objective of the study was to evaluate cytotoxic activity of essential oils using cancer cell lines and antitumor activity against Ehrlich Ascites Carcinoma transplanted Swiss albino mice. Materials and Methods: Lemon oil and jasmine oil were tested for their In vitro cytotoxicactivity against the mouse fibroblast (L929) cell line and urinary bladder (RT4) cell lineusing MTT Assay as well asIn vivotumorstudies werecarried out to access the chemo preventive effect of lemon oil and jasmine oil through intraperitoneal transplantation of EAC in a healthy adult Swiss albino mice. Results: Among the essential oils,lemon oil showed statisticallysignificant (*** P< 0.0001) cytotoxic activitytowards L929 cell lineRT4 cell line as compared to standard.Whereas jasmine oil exhibited statistically significant (*** P < 0.0001) cytotoxic activityonly towards RT4 cell line and were insignificant towards L929 cell line compared to standard.On EAC inoculated mice, lemon oil showed significant (**P < 0.001) reduction in the volume of tumor as well as in weight of tumor with increase in mean survival time and % ILS (**P < 0.001 and ***P <0.0001) compared to tumor control. Jasmine oil additionally reported slightreduction in tumor volume and tumor weight and were insignificant, but showed significant increase in hemoglobin count (*P < 0.0001), as well as in mean survival time and % ILS (**P < 0.0001) compared to tumor control. Conclusions: Lemon oil has showed significant cytotoxic activity towards mouse fibroblast cell lineand urinary bladder cell line compared to jasmine oil and on EAC inoculated mice lemon oil at a dose of 400mg/kg showed significant reduction in the tumor volume as well as tumor weight and significant increase in hemoglobin count compared tumor control. Whereas jasmine oil showed significant cytotoxic activity only towards urinary bladder cell line and on EAC inoculated mice, jasmine oilat a dose of 400mg/kg significantly reduced the eosinophil count compared tumor control.Both the oils showed significant increase in MST and % ILS.