Objective: To evaluate the anticancer effect of Carica papaya in DMBA induced mammary tumors in rats. Methods: Wistar rats were divided in to five groups (n=6), Group-I (Normal control) administered vehicle olive oil, Group-II, Group-III ,Group-IV and V induced mammary tumors by administering single dose of DMBA (7,12 Dimethyl benz(A)anthracene) orally 65 mg/kg. Group-III was administered aqueous leaf extract of Carica papaya (ALQECP) in a dose of 200 mg/kg body wt for a period of 3 months, group-IV has given ALQECP 200 mg/kg body wt for a period of 21 days post 3 months of tumor induction, group-V rats were administered a small dose of Carica papaya extract intra tumor locally in the region of tumor. Results: Values of CA15-3 were increased in group-II rats (tumor control) significantly, whereas in group-III (prevention group) the levels of CA15-3 were found to be reduced substantially and the P value < 0.001. Similarly, CA-15-3 levels were reduced significantly in group-IV (treatment group)and P<0.005. The levels of LDH were seen to be increased in group-II, where as in group-III LDH levels were decreased and P<0.001.similarly group-IV LDH levels also reduced significantly but not to the level of group-III. Conclusion: Among the various markers for the detection of cancer antigen- 15(CA15-3) and lactate dehydrogenase (LDH) are important biochemical parameters that give a clear understanding of the progression and proliferation of cancer cells. In this study it was found that there is increase in the levels of markers such as CA15-3 and LDH and also the tumor volume in tumor control, these marker levels were decreased by the administration of aqueous leaf extract of Carica papaya in a dose of 200 mg/kg body wt. ALQECP not only prevented the progression of cancer growth but also has significant effect in reducing the both CA15-3 and LDH levels in treatment group.