The thyroid gland has some important endocrine hormones that regulate basal metabolism in various tissues of domestic animals. Thyroid hormones have a central role in animals' development and their tissue functions. In this study, the relationship between the plasma thyroxine (T 4 ), triiodothyronine (T 3 ), free thyroxine (fT 4 ), free triiodothyronine (fT 3 ), triglyceride, cholesterol, glucose, total protein, and albumin concentrations as well as albumin/globulin ratio in different ages of Iranian Sarabi calves was investigated. Blood samples were collected from the jugular vein of 47 clinically healthy calves free from internal and external parasites (grouped according to their age-1-14 days, 1-2, and 3-6 months) in early of winter. The level of thyroid hormones was determined by chemiluminescence, and other parameters were measured by spectrophotometry using commercial kits. Our data from this study indicates that there was no significant difference and correlation in all the studied parameters between age groups and sexes. But we found a significant correlation between plasma T 4 and total protein (P<0.05, r=0.600), T 4 and albumin (P<0.05, r=0.575), T 3 and fT 3 (P<0.05, r= 0.610), T 3 and total protein (P<0.01, r=0.725), T 3 and glucose (P<0.01, r=0.685), and fT 4 and fT 3 (P<0.05, r= 0.609) concentrations as well as between total protein and albumin/globulin ratio (P<0.01, r=−0.783).