Although statin therapy is beneficial in the setting of acute coronary syndrome (ACS), a substantial proportion of patients with ACS still do not receive the guideline-recommended lipid management in contemporary practice. We hypothesize that the low-density lipoprotein cholesterol (LDL-C) level at the time of admission might affect patient management and the subsequent outcome. Nine-hundred and forty-two consecutive patients with ACS who underwent percutaneous coronary intervention were analyzed retrospectively. The study patients were first divided into two groups based on the LDL-C level on admission: group A (n = 267), with LDL-C < 100 mg/dL; and group B (n = 675), with LDL-C ≥ 100 mg/dL. Each group was then further divided into those who were prescribed statins or not at the time of discharge from the hospital. The primary endpoint was all-cause death. In addition, we analyzed the serial changes of LDL-C within 1 year. Patients in group A were significantly older and more likely to have multiple comorbidities compared with group B. The proportion of patients who were prescribed statin at discharge was significantly smaller in group A compared with group B (57.7 vs. 77.3%, p < 0.001). During the median 4-year follow-up, there were 122 incidents of all-cause death. Multivariate Cox proportional hazard analysis revealed that LDL-C < 100 mg/dL on admission [hazard ratio (HR), 1.61; 95% confidence interval (CI), 1.09–2.39; p < 0.05] and prescription of statins at discharge (HR, 0.52; 95% CI, 0.36–0.76; p < 0.001) were associated significantly with all-cause death. Under these conditions, increasing LDL-C levels were documented during follow-up in those patients in group A when no statins were prescribed at discharge (79 ± 15–96 ± 29 mg/dL, p < 0.001), whereas these remained unchanged when statins were prescribed at discharge (79 ± 15–77 ± 22 mg/dL, p = 0.30). These results demonstrate that decreased LDL-C on admission in ACS led to less prescription for statins, which could result in increased death, probably due to underestimation of the baseline LDL-C.