The effect of dietary conjugated linoleic acid isomers (CLA) on growth performance, carcass composition, fatty acid composition of adipose and muscle tissues, and serum lipoproteins was investigated in broiler chickens. A total of 160 (eighty male and eighty female) chickens were allocated to four dietary treatments (0.0, 0.5, 1.0, and 1.5 % CLA) and fed a standard starter diet from 8 to 21 d, and a grower-finisher diet from 22–42 d. When determined for the total period 8–42 d, feed intake and body weight gains of broiler chickens were significantly reduced (from 3.31 to 3.12 kg and from 1615 to 1435 g respectively; P<0.05), particularly at the 1.5 % dietary CLA level. Feed conversion efficiency and carcass yield values showed no significant effects of dietary CLA. Abdominal fat deposition was significantly reduced (from 2.68 to 1.78 %; P<0.05), the relative proportion of breast muscles was unaffected, and that of leg muscles significantly increased (from 19.0 to 20.6 %; P<0.05). The concentration of CLA isomers (% of total methyl esters of fatty acids) increased linearly in tissue samples from broilers fed 0.5, 1.0, and 1.5 % dietary CLA. The relative proportions of saturated fatty acids (16:0, 18:0) were significantly (P<0.01) increased, and those of monounsaturated (16:1, 18:1) and polyunsaturated fatty acids (18:2, 20:4 in muscle tissues) significantly (P<0.05) reduced. Total serum cholesterol concentrations reached a maximum in broilers fed 1.0 % CLA and then decreased slightly (from 141.73 to 136.47 mg/dl; P<0.01). The same was true also for HDL-cholesterol (from 113.58 to 109.97 mg/dl; P<0.01). The HDL cholesterol:total cholesterol ratio and serum triacylglycerol concentration was unaffected. In conclusion, feeding CLA to broiler chickens resulted in substantial incorporation of CLA isomers into their tissue lipids, thus providing a potential CLA-rich source for human consumption.