Thyroid hormones and body metabolism are closely linked, therefore thyroid gland disturbance will affect the body's metabolism The purpose of this study is to compare the changes in oxidative stress biomarkers, biochemical, and hematological parameters in the serum of hypothyroid dogs and euthyroid dogs as controls. Thirty-three dogs ranging in age from 3 to 6 years were used in this study (20 hypothyroid and 13 euthyroid dogs). Assessment of thyroid hormone levels and clinical manifestations was enrolled to diagnose hypothyroidism. Each animal's serum was collected for assessment of free T4 (fT4), total T4 (TT4), thyroid-stimulating hormone (TSH), evaluation of Malondialdehyde (MDA), total antioxidant capacity (TAC) and catalase, selected trace and major minerals, cholesterol triglycerides, blood glucose, alkaline phosphatase (ALP), liver enzymes (ALT, AST, GGT), and hematological pictures. Laboratory results for hypothyroid and euthyroid dogs were compared. In hypothyroid dog's oxidative biomarkers showed non-significant changes in both MDA and TAC and a significant decrease in catalase. Zinc, iron, and calcium showed a significant decrease, but phosphorus showed a significant elevation, the lipid profile showed a significant elevation of cholesterol, triglycerides, LDL, and VLDL, while HDL showed non-significant changes. ALT, AST, and ALP are significantly increased, Hematological blood pictures RBCs, HGB, HCT, and RDWc were significantly deceased, MCHC, MONO, and BASO cells were increased significantly. The results showed that hypothyroidism is associated with considerable changes in oxidative, biochemical and hematological parameters in dogs, highlighting their importance in the assessment and follow up of canine hypothyroidism.