Abstract: The phytochemical composition of the tigernut tuber and the effect of the aqueous extract on some biochemical parameters such as blood glucose, serum protein, albumin and cholesterol, white blood cells, red blood cells, haemoglobin, erythrocyte sedimentation rate and packed cell volume were determined in rats administered different concentrations of the extract. From the result of the phytochemical analysis, the presence of alkaloids, cyanogenic glycosides, resins, tannins, sterols and saponins were observed in the raw tuber, however only alkaloids, sterols and resins were observed in the roasted tuber. Analysis of the antinutrient composition yielded oxalates (0.25±0.65 g/100 g), phytate (1.97±0.81 mg/100 g), saponins (0.88±0.02/100 g), tannins (9.50±0.46 mg/100 g) and cyanogenic glycosides (1.80±0.69 mg/100 g). Roasting numerically decreased the levels of the anti-nutritive factors analyzed. At the end of the treatment period, the mean weights of the animals increased. The blood glucose level decreased significantly in concentration dependent manner (p<0.05) and serum albumin level increased significantly in a concentration dependent manner (p<0.05) in the groups administered the different concentrations of the extract. There was no significant effect (p>0.05) on serum cholesterol and protein and on total and differential white blood cell, red blood cell, haemoglobin, packed cell volume and erythrocyte sedimentation rate. The results therefore indicate the absence of undesirable effect in the use of the tigernut tuber even in the raw form at least at the administered concentration and for the duration of feeding. The findings are of nutritional, health and industrial relevance since the tuber is currently being used as food in many homes in Nigeria.