Most of the thalassemic children of Bangladesh are receiving repeated blood transfusion. But they do not receive chelation therapy due to financial constraints. As a result, iron overload occurs in various organs of these children. Extra iron that is loaded in thyroid gland causes thyroid dysfunction. This study was undertaken to evaluate thyroid status in children with transfusion dependent Thalassemia patient. This cross-sectional analytical study was conducted in the Department of Pediatrics, Mymensingh Medical College Hospital, Bangladesh from September 2016 to April 2018. Children having thalassemia diagnosed by Hb electrophoresis, aged 3-12 years of both sexes were included as study group. Children of same age and sex admitted in indoor of Mymensingh Medical College Hospital with minor illness and without thalassemia were taken as comparison group. Purposive Sampling technique was applied. Serum FT₄, TSH and ferritin level were estimated in all children. Data analysis was done with Statistical Package for Social Science (SPSS) version 21.0. A total of 60 patients were enrolled as study group and another 60 patients were compared as comparison group. Mean ages of study group was 7.88±2.55 years and comparison group were 7.22±2.48 years. The mean pre-transfusion hemoglobin, serum ferritin, serum FT₄ and serum TSH level were found 6.23±0.60 gm/dl, 2658.33±879.39 ng/ml, 15.14±4.40 fmol/mL, 4.29±4.60 μIU/mL respectively in study group. The mean serum FT₄ was found significantly lower and mean serum TSH was significantly higher in thalassemic children in comparison to non-thalassemic children (p= <0.05). Frequency of subclinical hypothyroidism was found significantly higher in study group (25.0%) compared to comparison group (3.3%) (p=0.001). Mean serum ferritin level was found significantly higher in hypothyroid cases. Mean FT₄ level was significantly lower and mean TSH level was significantly higher in hypothyroid thalassemic patients (p= <0.001). Significant positive correlation between serum ferritin level and serum TSH level was found. Higher serum ferritin level was found significantly associated with the development of hypothyroidism in thalassemic patients.