Abstract: Present study was performed to determined the changes in the blood picture of the brown rats Rattus norvegicus naturally infected with intestinal cestodes. The results are based on the examination of 82 brown rats captured at random from Hyderabad city and its adjacent areas. Blood profiling of cestode (Hymenolepis diminuta and Hymenolepis nana) infected male and female rats showed significantly lower values of Total Erythrocyte Count (TEC), Haemoglobin (Hb) concentration, Haematocrit (Hct), Mean Corpuscular Haemoglobin (MCH) and Mean Corpuscular Haemoglobin Concentration (MCHC) as compared to their control (non-infected) rats of both sexes. The Mean Corpuscular Volume (MCV) value for infected male and female rats was found significantly higher than those of their control rats. A significantly higher Total Leukocyte Count (TLC) in male and female infected rats was noted as against the non-infected (control) rats of both sexes. The Differential Leukocyte Count (DLC) revealed significant increase in absolute number of each type of cell in cestode infected male and female rats. However, lymphocyte and basophil counts recorded from male infected rats were similar to the counts of their control rats. Conspicuous changes in the blood picture of cestode infected male and female rats indicate host-parasite interaction as well as the triggering of defense mechanism in the host against infection.