To investigate the potential role of fresh Carica papaya (C. papaya) leaf extract on haematological and biochemical parameters and toxicological changes in a murine model.In total 36 mice were used for the trial. Fresh C. papaya leaf extract [0.2 mL (2 g)/mouse] was given only to the test group (18 mice). General behavior, clinical signs and feeding patterns were recorded. Blood and tissue samples were collected at intervals. Haematological parameters including platelet, red blood cell (RBC), white blood cell (WBC), packed cell volume (PCV), serum biochemistry including serum creatinine, serum glutamic-oxaloacetic transaminase (SGOT) and serum glutamic-pyruvic transaminase (SGPT) were determined. Organs for possible histopathological changes were examined.Neither group exhibited alteration of behavior or reduction in food and water intake. Similarly, no significant changes in SGOT, SGPT and serum creatinine levels were detected in the test group. Histopathological organ changes were not observed in either group of mice except in three liver samples of the test group which had a mild focal necrosis. The platelet count (11.33±0.35)×105/μL (P=0.000 04) and the RBC count (7.97±0.61)×106/μL (P=0.000 03) were significantly increased in the test group compared to that of the controls. However, WBC count and PCV (%) values were not changed significantly in the test group. The platelet count in the test group started to increase significantly from Day 3 (3.4±0.18×105/μL), reaching almost a fourfold higher at Day 21 (11.3×105/μL), while it was 3.8×105/μL and 5.5×105/μL at Day 3 and Day 21 respectively in the control. Likewise, the RBC count in the test group increased from 6×106/μL to 9×106/μL at Day 21 while it remained near constant in the control group (6×106/μL).Fresh C. papaya leaf extract significantly increased the platelet and RBC counts in the test group as compared to controls. Therefore, it is very important to identify those chemicals of C. papaya leaves as it can be recommended to be used as a medication to boost thrombopoiesis and erythropoiesis in humans and in animals in which these cell lineages have been compromised.