OBJECTIVES: Patients receiving enoxaparin are at risk of bleeding. However, the study of the financial impact of enoxaparin-associated bleeding is limited. This study aims to estimate the attributable costs and length of stay (LOS) of patients with enoxaparin-associated bleeding (EAB) compared with non-bleeding patients (NB). METHODS: We conducted a retrospective cohort study of hospitalized acute coronary syndrome patients who received enoxaparin since January 2006 to February 2009 in a large University-affiliated hospital. Cost and LOS were compared between patients with and without EAB on both univariable and multivariable analyses. In multivariable analysis, the attributable cost and LOS were estimated using a multiple linear regression with log-transformed model and adjusted by propensity score (PS), which was predicted by patient’ characteristics  including age, gender, history of bleeding, hypertension, stroke, diabetes, creatinine clearance and congestive heart failure (CHF) at admission. The adjusted means of cost and LOS estimates were retransformed to their natural values using Duan’s smearing estimator. The differences of costs and LOS were presented as mean with 95% confidence intervals. RESULTS: Out of 346 patients, 134 (38.7%) experienced enoxaparin-associated bleeding. The average age and co-morbidities in both groups were similar. However, in EAB group had more male than NB group (42% vs 30%). Based on univariable analyses, the attributable cost and LOS of patients with EAB were 68,875 THB ($2,152) and 4.2 days, respectively. Based on PS-adjusted multivariable regression analyses, the cost and LOS attributable to EAB was 80,644 THB ($2,520) (95%CI: 69,879 ($2,184) to 91,408 ($2,857) and 3.4 days (95%CI: 3.0 to 3.7), respectively. CONCLUSIONS: Bleeding is associated with increased cost and LOS among enoxaparin users. These findings suggest that strategies that reduce the risk of bleeding have the potential important reductions in costs of care for enoxaparin users.