The effects of vinasse supplementation on broiler performance, abdominal fat deposition, blood and tibial parameters, morphology and histology of various organs of broilers were studied. A corn- soy meal-based diet was used without vinasse as control, Vinasse was added at low (2.5%) and high levels (5%). Three hundred and thirty day-old (Cobb) broiler chicks were divided into three treatments using 55 broilers in each group (experiment I and II). The live weights were lower in the experimental group (5% vinasse) than in the control group on the 1(st), 2(nd) and 3(rd) week (131, 357 and 710g, respectively) (experiment I). However, the main effect of added 2.5% vinasse on weight gain was significant (p < 0.05) from days of age 7 to 14 and 14 to 21. No difference was observed on days 42 (experiment I) and 35 (experiment II) for body weight by feeding vinasse at 2.5% and 5% levels, respectively. Feed intake and feed conversion of the broilers was not improved in both experiments. In experiment I, abdominal fat percentage was lower in the experimental groups than in the control group (1.40, 1.42 and 1.60, respectively) (p < 0.05). Carcass yields were higher in the experimental groups than in the control group (76.99, 75.87, 74.08, respectively, p < 0.05). In experiment II, the level of vinasse in the diet had no effect on the carcass characteristics of broilers (p > 0.05). In experiment I, biochemical parameters analyzed in serum samples were significantly different between control and experimental groups (p < 0.05). Total lipid, calcium, phosphorus, sodium, and potassium levels were found to be higher in the experimental group than in the control group. Total cholesterol levels were lower in the experimental group compared to the control group. In experiment II, serum samples did not indicate any differences between control and the experimental groups, except for total lipid and phosphorus. Tibia analyses showed that ash percentage was markedly increased at the highest vinasse dose (5%), but there were no significant differences in the phosphorus and calcium concentrations of the tibia. In experiment I livers of six birds of the first trial group (2.5% vinasse) and five birds of the second group (5% vinasse) were slightly yellowish and contained foci of petechial hemorrhages on their surface. In experiment II for birds on 2.5% vinasse and for birds on 5% vinasse yellowish and friable livers containing linear or petechial hemorrhages on their surface and hyperemic kidneys were observed. It can therefore be concluded that vinasse addition to feed from 2.5% to 5% does not have any adverse effects on poultry, but the conditions for uniform dispersion must be provided, otherwise toxic effect can be observed.