Chlorambucil is an anticancer drug with alkylating and immunosuppressive activities. Considering various reports on the possible antioxidant/protective functions of ascorbic acid (vitamin C), it was aimed at to explore the modulatory effect of ascorbic acid on therapeutic efficacy and toxicity induced by chlorambucil. Dalton's ascites lymphoma tumor serially maintained in Swiss albino mice were used for the present experiments. The result of antitumor activity showed that combination treatment with ascorbic acid and chlorambucil exhibited enhanced antitumor activity with 170% increase in life span (ILS), which is significantly higher as compared to chlorambucil alone (ILS 140%). Analysis of apoptosis in Dalton's lymphoma tumor cells revealed a significantly higher apoptotic index after combination treatment as compared to chlorambucil alone. Blood hemoglobin content, erythrocytes and leukocytes counts were decreased after chlorambucil treatment, however, overall recovery in these hematological values was noted after combination treatment. Chlorambucil treatment also caused morphological abnormalities in red blood cells, majority of which include acanthocytes, burr and microcystis. Combination treatment of mice with ascorbic acid plus chlorambucil showed less histopathological changes in kidney as compared to chlorambucil treatment alone, thus, ascorbic acid is effective in reducing chlorambucil-induced renal toxicity in the hosts. Based on the results, for further development, hopefully into the clinical usage, the administration of ascorbic acid in combination with chlorambucil may be recommended.