The proportion of elderly acute coronary syndrome (ACS) patients who receive optimal medical therapy (OMT) after percutaneous coronary intervention (PCI) and whether OMT affects their long-term outcomes remain unclear. We retrospectively investigated 405 ACS patients who underwent stent implantation between 2005 and 2009, and compared the outcomes between patients <80 years of age vs. ≥80 years of age. The prescription rate of the recommended medical agents for ACS in both groups during hospitalization and 2 years after admission was also retrieved. Among the enrolled study population, 75 patients (19%) were aged ≥80 years. These elderly patients had a higher 2-year mortality compared with patients aged <80 years group. The prescription rate of beta-blockers, angiotensin-blocking drugs, and statins tended to be lower in patients aged ≥80 years than in those aged <80 years. Furthermore, among patients ≥80 years of age, those who received OMT had better clinical outcome of 2-year mortality compared to those without OMT. Elderly patients with ACS treated by PCI are at substantially higher risk of adverse events than younger patients. However, they are less likely to receive OMT. PCI with OMT might improve the clinical outcomes of elderly ACS patients.