Introduction : Insulin resistance (IR) has an important role in pancreatic -cell dysfunction and incidence of type-2 Diabetes Mellitus (DM-2), and such resistance is also able to indicate the pathophysiological component of other endocrine metabolic disorders such as hypertension, obesity, dyslipidemia, and cardiovascular disease (CVD). Obesity is a major risk factor for endothelial dysfunction which develops as a result of abnormal regulation of vasoactive substances including nitric oxide, where endothelial dysfunction is the starting point in the pathogenesis of IR. This study’s objective is to compare Admission Insulin Resistance Index (AIRI) values in Obese and Non-Obese Acute Coronary Syndrome patients. Methods: This was a cross sectional study with consecutive sampling method consisting of 60 subjects who were treated with Acute Coronary Syndrome at Dr. Wahidin Sudirohusodo Hospital Makassar, Indonesia from July-September 2020. Anthropometric examinations include measuring body weight and height to determine body mass index (BMI). AIRI was measured insulin admission (IU / ml) x plasma glucose admission (mg / dl) / 405. Statistical analyses used were Chi Square test and Spearman’s Correlation test ( significance p <0,01 ). Results: Average age of the subjects was 54.9 + 13.6 years old, with 76,7 % male. Based on the results of clinical, laboratory and ECG examination, the subjects had hypertension (48.3%), obesity (35%), decreased HDL (38.3%), increased triglycerides (28.3%), increased LDL (70%), increased RBG (76.7%), experienced IR (20%), diagnosed of STEMI (35%), NSTEMI (53.3%), and UAP (11.7%). There was a significant relationship between obesity and AIRI (p <0,001). Where in obese, it was found that the percentage of AIRI's tertile 3 (70%) was the highest compared to AIRI's tertile 2 (20%) and AIRI's tertile 1 (15%). Meanwhile, those who were not obese were found to have the highest level of 1 AIRI (85%) compared to 2 AIRI (80%) and 3 AIRI (30%). Conclusion: Obesity in patients with ACS is related to the AIRI value.