The current study investigated the impact of different concentrations of purified egg yolk immunoglobulin Y (IgY) supplemental food on the growth performance, behaviors, cecal contents of Escherichia coli, and the meat quality of broiler chicks. Four dietary groups were given to 180 female Ross broiler chicks at random (n = 45 for each). The control group was fed a standard diet only, whereas the other three experimental groups were fed the same basic diet supplemented with 1,500, 3,000, and 4,000μg/ml IgY for a duration of 42 days. Significant greater behavioral activities, including, feeding, drinking, and dust bathing (p < 0.05), in the birds fed 4,000μg/ml of IgY compared to the control group were observed. Greater weight gains of the crop, proventriculus, gizzard, and intestine (p < 0.05) were observed for broiler chicks fed 4,000μg/ml of IgY when compared to the control group. After 3 weeks of feeding, the groups fed 3,000 and 4,000μg/ml IgY had significant lower E. coli counts in the muscle and cecal contents (p < 0.05) when compared to the control group. Moreover, dietary supplementation with 4,000μg/ml IgY in the third week and 3,000μg/ml IgY in the sixth week resulted in greater weight gain (p < 0.01) when compared to the control group. Also, at week 3, chicks fed 4,000μg/ml of IgY had a lower feed conversion ratio (FCR) when compared to Rehan et al. IgY-Concentrations Improved Meat Quality the control group (p<0.05). At week 6, chicks fed 3,000μg/ml of IgY had lower FCR than the control (p < 0.05). The circulating heterophile/lymphocyte ratio was simply altered in birds fed variable IgY concentrations (1,500, 3,000, and 4,000μg/ml), with no significant differences compared to the control group due to the individual resistance of each bird to physiological stress. The addition of 4,000μg/ml IgY to the diet enhanced the nutritive value of meat, including protein, fat, and ash content (p < 0.05). Our study concluded that dietary supplementation of 3,000 and/or 4,000μg/ml IgY improved the growth rates, behavioral activities, intestinal health indices, and meat quality of broiler chicks