In cardiovascular homeostasis thyroid hormone plays an important role. We planned to study the changes in thyroid hormone profile in acute coronary syndrome patients admitted in the coronary care unit and compare them between two groups: unstable angina/non-ST elevated Myocardial infarction (UA/NSTEMI) and ST elevated Myocardial infarction (STEMI). This study was a hospital based descriptive cross sectional study which was conducted from 01 March 2018 to 01 February 2019 in Coronary Care Unit of Bangladesh Medical College Hospital and laboratory tests were done in Microbiology Department of Bangladesh Medical College, Dhaka, Bangladesh. Eighty three cases of acute coronary syndromes were taken for the study. Troponin-I was measured as cardiac marker, Electrocardiogram, Complete blood count, blood glucose level, Blood urea, serum creatinine, serum electrolytes, Fasting lipid profile, Thyroid profile, Echocardiography 2D were done. Most of the respondents were distributed in age group 46-60 years where 34(64.15%) male and 19(35.85%) female. Out of 83 Acute Coronary Syndrome (ACS) patients, 27(32.53%) hypertensive, 22(26.50%) diabetic and 16(19.27%) were Chronic kidney disease (CKD). Abnormal lipid profile was present in 30(43.47%) patients. Among total 52 male and 31 female 9(17.30%) male and 6(19.35%) female had abnormal thyroid function. We further elaborated abnormal thyroid function tests in STEMI group and UA/Non STEMI group of ACS patients. We found 10 patients in STEMI group and 5 patients in UA/Non STEMI group with abnormal thyroid function 29.41% and 10.20% respectively which was not statistically significant (p=0.025). This study depicts abnormality in thyroid hormone profile in 18.07% patients of ACS. Abnormal thyroid function increases risk of coronary artery disease. TSH level of ACS patients on hospital admission could be helpful to evaluate further prognosis of the disease.