Epidemiological studies have demonstrated an association between low serum albumin levels and coronary heart disease and mortality. Nevertheless, the impact of a low serum albumin level during acute coronary syndrome has not yet been established. The aim of the present study was to investigate whether low serum albumin levels are associated with adverse outcomes in acute coronary syndrome. We enrolled 82 consecutive patients with acute coronary syndrome from whom venous blood for serum albumin measurement was drawn immediately upon hospital admission. Thirty-five patients had a low albumin level (hypoalbuminemia) and 47 had a normal albumin level (normoalbuminemia). In-hospital adverse outcomes (death, acute heart failure, cardiogenic shock, and reinfarction) were recorded during hospitalization in the intensive coronary care unit. The results of our study showed that the incidence of in-hospital adverse outcomes was 43%, with death occurring in 8 patients (10%). In-hospital adverse outcomes occurred more frequently in patients presenting with hypoalbuminemia, whereas mortality did not differ significantly. Univariate analysis showed that hypoalbuminemia was associated with a 2.8-fold greater risk of developing adverse outcomes. This risk was greater in the subgroup of NSTEACS (5.4-fold increased risk), but not in those with STEMI. Adjustment with other covariates revealed that hypoalbuminemia did not predict independently in-hospital adverse outcomes. It interacted with other predictors, especially Killip class II-IV, which was consistently an independent predictor of in-hospital adverse outcomes.