Diabetes mellitus is a global health problem affecting major populations worldwide. It is a group of metabolic disorders characterized by absolute or relative deficiencies in insulin secretion with chronic hyperglycaemia and disturbances of carbohydrate, lipid, and protein metabolism. Thyroid hormones are secreted from thyroid gland. Thyroid hormone replacement is associated with a decrease in Glycated Hemoglobin (HbA1c) level. The present study was undertaken to study correlation between thyroid profile and glycated Haemoglobin (HbA1c) in Type 2 Diabetes Mellitus patients. A hospital based case control study was carried out in Dept. of Biochemistry, North Bengal Medical College, Sirajganj, Bangladesh from July to December 2022. 100 participants were in the study group and 100 participants in control groups were enrolled by following procedure. Patients aged 30 years or more who came to routine health check-up were taken for the study. Basic information, clinical history was taken from the record files. 50 cases of Type 2 Diabetes mellitus and 50 healthy controls were taken. Blood samples were collected and analyzed for thyroid profile, HbA1c, Fasting Blood Sugar and Renal Function Test. We found that there was a positive correlation between TSH (Thyroid stimulating hormone) and HbA1c levels, and a negative correlation between Thyroid hormones [Triiodothyronine (T3) & Thyroxine (T4)] and Glycated Haemoglobin (HbA1c) in cases of type 2 Diabetes Mellitus. There is a significant decrease in TT3 (Total Triiodothyronine) and TT4 (Total Thyroxine) and significantly increased TSH in cases of Diabetes mellitus as compare to healthy Controls. We found that out of 50 cases of type 2 Diabetes Mellitus, 31% patients showed thyroid disorders. There is a high prevalence of thyroid disorders in Diabetic patients. If not diagnosed early, it could negatively affect diabetes and its complications. Therefore, routine screening of thyroid profile in diabetic patients is advisable to improve quality of life and reduce morbidity rate.