In this study, changes in the hematological parameters and immunoglobulin levels of sheep fed different diets were investigated. Healthy, nonpregnant, female Norduz sheep age 1 - 2 years with live weights of 50 - 55 kg that were raised at the Agricultural Research and Implementation Center of Van Yuzuncu Yil University constituted the animals used in this study. A total of 40 sheep comprised three groups: a control group (n = 20) and two experimental groups (n = 10 in each group). During daylight hours, the sheep grazed primarily on low-quality pasture and lesser amounts of grass. In addition to pasture grazing, all groups were supplied with 850 g d-1 of mixed grass-clover hay per head. Aside from pasture grass and mixed grass-clover hay, the control group animals were also supplied with 50 g d-1 of barley per head. Each animal in the experimental group (groups 1 and 2) was also supplied with increasing amounts of barley each week: 65 g d-1, 95 g d-1, 110 g d-1, and 130 g d-1 in the first, second, third, and fourth weeks, respectively. Aside from pasture grass, mixed grass-clover hay and barley, animals from the second group were also supplied with 500 g d-1 of concentrated feed per head throughout the experiment (4 weeks). This study revealed that improved dietary quality causes significant increases in hematological parameters and immunoglobulin levels. The results showed that the hematocrit levels, mean corpuscular volumes, and mean corpuscular hemoglobin concentration values of group 2 were higher than those of the other groups (P<0.05 for hematocrit; P<0.01 for other comparisons). The diets enriched with the concentrated feed increased the immunoglobulin A, immunoglobulin G, immunoglobulin E, and immunoglobulin M levels in sheep compared with levels in the control group (P<0.01). Improvements in these values will reduce the risk of disease in animals and naturally increase their productivity.