One hundred and eighty (180) unsexed twenty-one day-old growing Japanese quails (Coturnix coturnix japonica) were fed for 28 days with diets in which maize was replaced with cassava grit at 0, 25 and 50% with or without β-glucanase supplementation. The birds were randomly grouped into six treatments in three replicates of ten birds per replicate. Diet 1 was the control without cassava grit while diets 2 and 3 had 25 and 50% of their maize contents replaced with cassava grit respectively. Diets 4, 5 and 6 were the same as diets 1, 2 and 3 respectively but for the inclusion of β-glucanase at 100mg/kg. Feed and water were supplied ad libitum throughout the period of study. Feed intake (590.98g), weight gain (93.77g) and FCR (6.35) were significantly (p<0.05) affected by the dietary treatments. 6 Among the haematological parameters monitored RBC (4.46x10 /UI) and WBC 3 (26.52x10 /UI) were significantly (p<0.05) affected by dietary treatments. Thiocynate (2.57 mg/ml), AST (290.6 U.I/L) and ALT (33.6 U.I/L) were also significantly (p<0.05) influenced by the experimental diets. Replacement of 25 or 50% maize with cassava grit in diets of the Japanese quail diets did not have negative effect on haematology and serum biochemistry of the birds. There were however significant differences (p< 0.05) affected by the treatments while caeca length and the lungs weight were statistically similar across the treatments. Replacement of maize with cassava grit at 25 and 50% in Japanese quail diets had no negative effect on haematology, serum biochemistry and carcass characteristics of the birds.