This study was conducted to investigate the effects of feeding herb extract (HE) on productivity, intestinal microflora and blood component profile in broiler chickens. A total of three hundred twenty, 1-d-old male chicks (Ross) were divided into 4 treatments with 5 replicates, 16 birds per replicate. Dietary treatments consisted of four diets; the corn-soybean based control diet, the diet containing HE 0.1%, the diet containing HE 0.2%, and the diet containing HE 0.4%. The Control diet contained 3,100, 3,100, 3,200 kcal/kg ME and 22%, 20%, 18% CP for starter (0~2 wk), grower (3~5 wk), and finisher (6~7 wk) periods, respectively. There were no significant differences in feed intake and BW gain among treatments in starter period. In grower period, the BW gain of HE 0.2%, and HE 0.4% were significantly higher (p<0.05) compared to Control. The 7-wk BW gain of HE 0.2% was significantly higher than Control (p<0.05). The feed intake tended to increase in HE 0.1%, but no difference was detected in feed conversion ratio among treatments. No significant differences were found in blood total cholesterol, triglyceride, HDL-cholesterol, glucose, total protein, and albumin among treatments, but total cholesterol in HE 0.4% decreased significantly as compared with Control. The cfu of Lactobacillus spp., yeast, and E. coli in the guts of chickens fed HE were not different form each other, but tended to increase as compared with Control.