The effects of sub-acute exposure to aqueous extract of Parkia biglobosa seeds on haematology and plasma biochemical parameters were studied. Twenty eight male Wistar albino rats were orally ingested with 0, 200, 400 and 800 mgkg -1 dose of the extract for 21 days and were sacrificed. Haematological parameters were assessed: red blood cell counts, haematocrit and haemoglobin concentration significantly (p<0.05) increased at the 800 mgkg -1 dose. We also observed significant increases in white blood cells, lymphocytes and neutrophils at this dose. Evaluation of effect of seed extract on plasma biochemical values revealed significant increase in total protein, albumin and aspartate amino transferase. However, the extract caused significant decrease (p < 0.05) in the levels of blood urea nitrogen and creatinine. Changes observed in plasma levels of globulin, alanine amino-transferase (ALT) and gamma-glutamyl transferase (GGT) were not significantly different from the control at all treatment doses.