Introduction: The prevalence of obesity in all age groups has increased dramatically over the past 30 years, such that overweight and obesity are considered to be a major public health concern in many countries. Obesity affects hypothalamic-pituitary-thyroid axis directly or indirectly leading to alterations in thyroid function tests. Aim of the study: To evaluate thyroid function in obese children and to correlate it with different parameters. Subjects and methods: This study included two groups; Group Ι: 40 obese patients where obesity was defined according to the body mass index (BMI) above the 95th percentile for age and sex using the definition of the International Task Force for obesity in Childhood and Group Π: 40 children age and sex matched as a control group. They were subjected to: Thorough history taking, clinical examination, anthropometric measurements and laboratory investigations including; fasting blood sugar, total cholesterol and triglycerides, thyroid Function Tests (TSH, free T3, free T4 and anti- thyroglobulin anti-bodies (Tg-Ab). Results: 35% and 40% of obese children had increased serum levels of TSH and free T3 respectively. Also, there were significant differences between cases and controls as regard: TSH, free T3 and insignificant difference as regard free T4. None of our patients had anti TG titre positivity. There were significant correlations between TSH with BMI, triglycerides and cholesterol while there was insignificant correlation between fT3 with BMI. Conclusion: Some obese children show thyroid function tests abnormality in the form of increased TSH and fT3. Furtherly, none of them show anti TG positivity values. So, thyroid autoimmunity does not play a significant role in thyroid changes noted in obese children.