In This study, 48 broiler chicks were used in 8 groups to evaluate the optimum time of pre-slaughter feed withdrawal (FW) for broiler chickens in order to investigate the effect of different pre-slaughter feed withdrawal periods (0.0, 4.0, 8.0 and 12.0 h) and live body weight grade at slaughter (grade A₁ from 1800 to 2000g and grade A₂ from 1600 to 1800g) on weight loss, carcass parts, carcass traits, giblets weight, gizzard content weight, water holding capacity (WHC) and pH values of breast and thigh meat. Some blood plasma constituents (glucose, triglycerides, uric acid and total lipids) and chemical composition of meat as well as determining its effects on meat yield. The obtained results showed that both of relative and absolute weight loss, carcass parts, dressed carcass, protein and ash content of thigh and breast meat, WHC values were significantly (p≤0.01) increased gradually with the increasing of FW period from 0.0 up to 12.0 h before slaughtering. On the other hand, both of absolute and relative weight of abdominal fat, giblets and gizzard content, concentration of glucose, pH value and moisture and fat content of breast and thigh meat decreased as the FW period increased. It were observed that the higher values of plasma triglycerides and total lipids were recorded for broiler of 8.0 h FW experimental group. Results show that the weight grade had significant (p≤0.01) effects on the absolute weight of abdominal fat, carcass parts and dressed carcass, relative weight of giblets, chemical composition of meat and W H C and pH values. In the same way the relative weight loss, abdominal fat and thigh weight and concentration of glucose was significantly ( p≤0.05) affected by weight grade. However, absolute weight loss, gizzard content and giblets, as well as, relative weight of dressed carcass and concentration of uric acid, plasma total lipids and triglycerides were not significantly affected by weight grade. It was observed that the grade A₂ had higher values of relative weight loss, gizzard content and giblets than grade A₁ by about 7.9, 11.5 and 9.3%, respectively. In comparison the grade A₁ had higher values of absolute weight of abdominal fat, carcass parts and dressed carcass than grade A₂ by about 20.1, 16.5, 14.8 and 14.1%, respectively. This study revealed that the optimum feed withdrawal times pre-slaughter for broiler chickens ranging from 8.0 to 12.0 h showed the best results of carcass traits and quality. In addition, the slaughtering of broilers at 1600 – 1800g resulted in better values of the same traits than those slaughtered at 1800 – 2000g.