A 6-wk feeding trial with 240 day-old hubbard broiler chicks was conducted to study the effect of feeding diets containing Nigella seed meal on growth performance, some serum biochemical parameters and activities of some liver enzymes. During each feeding phase (starter, grower and finisher) isonitrogenous and isocaloric diets were formulated, where Nigella seed meal was included at three levels to supply amount of protein equal to 25,50 or 75% of the protein amount supplied by soybean meal in the control diet. The results showed that the use of Nigella seed meal to supply amount of protein equal to 25% of the protein amount supplied by soybean meal in the control diet has significantly (p < 0.01) increased final body weight, body gain, feed conversion ratio and feed efficiency, while no significant differences were detected when Nigella seed meal was used to supply 50 or 75 % of the protein amount supplied by soybean meal in the control dies. However, inclusion of Nigella seed meal in the broiler diets did not significantly (p > 0.01) affect the total feed consumption, although broiler chickens tended to consume more feed as the amount of protein supplied by Nigella seed meal in the diet increased, feed costs were relatively low when Nigella seed meal was used to supply amount of protein that would replace 25.50 or 75 % of the protein. Compared to the control, serum concentrations of T3 and T4 were significantly (p < 0.01) increased when Nigella seed meal was used to supply amount of protein that replaced 25.50 or 75 % of the protein amount supplied by soybean meal in the control diet., while glucose concentrations were significantly decreased. Serum concentrations of globulin were significantly (p < 0.01) elevated at all used levels of Nigella seed meal, while serum total protein concentration was significantly increased only when Nigella seed meal was used to supply 25 % of the protein. Triacylglycerol and total cholesterol concentrations were significantly reduced when Nigella seed meal was included in the diets to furnish amount of protein substituting 25, 50 or 75 % of the protein amount provided by soybean meal in the control diet, while high densitylipoproteins were significantly in creased only when 75 % of the protein amount supplied by soybean meal in the control diet was replaced by equal amount of protein provided by Nigella seed meal. Vitamin C and glycogen concentrations were significantly (p < 0.01) increased in hepatic tissues of chickens fed diets contained Nigella seed meal regardless of the amount used. The activity of liver enzymes (AST, ALT and GGT) were not significantly (p > 0.01) affected when either 25 or 50 % of soybean meal protein in the control diet was replaced by equal amount of Nigella seed meal protein, while the activity of these enzymes was significantly affected when 75 % of Nigella seed meal protein was used. Under the conitions of this study, it could be concuded that Nigella seed meal could be successfully used in broiler diets to supply amount of protein that could replace 25 % the protein amount supplied by soybean meal with favorable effects on growth performance, feed efficiency and biochemical parameters.