Background: Diabetes mellitus is an independent predictor of higher major adverse cardiac events (MACE) rate following percutaneous transluminal coronary angioplasty (PTCA) in acute coronary syndrome (ACS). Higher thromboxane production in diabetic patients has not been linked to aspirin resistance and recurrent events. Methods: This prospective observational cohort study aimed to investigate urinary 11-dehydro-thromboxane B2 (dh-TxB2) levels in diabetic and non-diabetic ACS patients undergoing PTCA and its association with MACE. The dh-TxB2 ELISA assay was performed during index admission in all patients, and they were followed-up for 1-year. Results: Out of the 192 patients enrolled, 84 (43.8%) were diabetic and 108 (56.2%) were non-diabetic. Median dh-TxB2 levels were higher among diabetics compared to non-diabetics [577.7 pg/mg Cr (IQR 991.2:62.8-1054.0) vs. 344.0 pg/mg Cr (IQR 691.4:73.4-764.8) respectively]. Patients with and without diabetes had 1-year MACE rates of 14.3% and 7.4% respectively (P=0.096). The patients who developed MACE had higher dh-TxB2 levels in both the groups [nondiabetics: 419.6 (non-MACE) vs. 1349.7 pg/mg Cr (MACE); p1496 pg/mg Cr developed more MACE than their counterparts in non-diabetics. The dh-TxB2 concentration may be used as a predictor of early MACE in diabetic ACS patients.