Abstract: Background and Objective: Blood disorders are frightful diseases because the patient suffers pain, disfigurement and loss of many physiological processes. In this study, the effects of ethanol extracts of Senna occidentalis leaves on haematological parameters in diethyl nitrosamine-induced toxicity was analyzed. Materials and Methods: In the experiment, 24 Wistar albino rats were divided into 4 groups of 6 rats each and toxicity was induced intraperitoneally by using diethyl nitrosamine (DEN) at 200 mg kg–1. Group one served as the normal control, group two was administered DEN only. Group three was administered DEN and ethanolic extract at 200 mg kg–1. Group four was administered DEN and silymarin (5 mg kg–1). The rats were sacrificed after 3 weeks of treatment. Blood samples were collected through cardiac puncture and used for hematological analysis; Red Blood Cell (RBC), White Blood Cell (WBC), platelets (PLT), procalcitonin test (PCT), Mean Platelet Volume (MPV), Platelet Distribution Width count (PDWc), haematocrit (HCT), Mean Cell Volume (MCV), Mean Cell Haemoglobin (MCH), Mean Cell Haemoglobin Count (MCHC) and red blood distribution width count (RDWc). Results: The DEN administration caused a significant increase (p<0.05) in RBC and HGB compared to the normal control and a significant decrease in PLT levels, whereas the concentrations of WBC, MID and GRA and LYM decreased significantly (p<0.05). Administration of ethanolic extracts/silymarin significantly (p<0.05) moderated the hematological indices. Conclusion: Due to its ability to moderate levels of haematological parameters, it is therefore, recommended for household management of blood related anomalies.