Background There is lack of evidence to assess the impact of hemoglobin level at presentation on long term prognosis after ACS. We investigated if hemoglobin on presentation affected cardiovascular outcomes in ACS over a 12- month period. Methods Clinical data at baseline and over a 12 month period were extracted for 160 consecutive patients admitted with a diagnosis of ACS. Primary endpoints were repeat event and all-cause mortality. Secondary endpoints were recurrence of significant angina (requiring ER visit/hospitalization), new onset left ventricular failure (LVF), new arrhythmia, composite of all cardiovascular complications, prolonged index hospitalization and repeat admission for cardiovascular causes. Results On univariate analysis, low hemoglobin was associated with prolonged index hospitalization (OR: 0.85, 95% CI: 0.74-0.98, p=0.02), repeat admissions (OR: 0.77, 95% CI: 0.66-0.90, p=0.001), composite cardiovascular complications (OR: 0.75, 95% CI: 0.63-0.88, p=0.005), recurrent angina (OR: 0.65, 95% CI: 0.54-0.78, p<0.001) and repeat event (OR:0.75, 95% CI: 0.59-0.97, p=0.03). There was no significant association of low haemoglobin with new-onset LVF (OR: 0.76, 95% CI: 0.60-1.01, p=0.08), new-onset arrhythmias (OR: 0.99, 95% CI: 0.62-1.56, p=.97) and all-cause mortality (OR: 0.84, 95%CI: 0.68-1.04, p=0.1). On a multivariate regression, low hemoglobin retained significant association with repeat admissions (r:0.4, p=0.02), composite cardiovascular complications (r:0.3, p=0.007), recurrent angina (r:0.5, p<0.001) and repeat events (r:0.2, p=0.06). Receiver-operating characteristic (ROC) curves showed significant discriminative ability of low hemoglobin for prolonged index hospitalization (area, 0.67; p=0.002), repeat admissions (area, 0.71; p<0.001), composite complications (area, 0.70; p<0.001), recurrent angina (area, 0.74; p<0.001) and repeat event (area, 0.70; p=0.01). Conclusions Low baseline hemoglobin in ACS patients predicts 12-month risk of repeat admissions, composite cardiovascular complications, recurrent angina and repeat event. This association appears independent of the infarct size and would justify closer follow up for these patients.