Several studies have shown that municipal solid wastes leachates are toxic using different biomarkers in plant and animal models. However, information is scarce on the haematotoxic effects of landfill leachates in mammals. In this study, the haematotoxicity of leachates from Olusosun and Aba-Eku landfills in Southwestern Nigeria in Wistar albino rats was investigated. Blood obtained from male and female rats exposed to 1 – 25 % concentrations of raw and simulated leachates was examined for alterations in haematological profiles. Aliquot of the blood samples was used to make smear for erythrocyte morphological evaluation. There was significant (p<0.05) reduction in red blood cell, platelets, total white blood cell counts, haemoglobin concentration, percentage haematocrit, mean corpuscle haemoglobin concentration, lymphocytes, monocytes, basophil and eosinophil concentrations; but significant (p<0.05) increase in mean corpuscle volume, mean corpuscle haemoglobin and neutrophils. Erythrocyte morphological lesions (p<0.05) included acanthocytes, echinocytes, schizocytes, tear drops and target cells. These observations showed sexual dimorphisms and were due to the constituents of the test samples. These show the potentials of landfill leachates to induce bone marrow impairment or direct damage to blood cells in rat probably via free radical formation and/or direct chemical damage to tissues. This may be of health risk in animal and human population expose to chemical substances from waste landfills.