Epidemiological studies have demonstrated an association between low serum albumin levels and both coronary artery disease (CAD) and mortality. However, the long-term clinical impact of low serum albumin level in patients with CAD undergoing percutaneous coronary intervention (PCI) has not yet been fully investigated. We studied 2860 all-comer patients with CAD who underwent their first PCI and had data available for pre-procedural serum albumin between 2000 and 2011. Patients were assigned to tertiles based on pre-procedural albumin levels. We evaluated the incidence of major adverse cardiac events (MACE), including all-cause death and nonfatal myocardial infarction. Mean albumin level was 4.0 ± 0.5 g/dL. Lower albumin levels were associated with older age, lower body mass index (BMI), and higher prevalences of female sex, ACS and chronic kidney disease (CKD). During the median follow-up period of 7.4 years, Kaplan–Meier curves showed ongoing divergence in rates of MACE among albumin tertiles (albumin <3.8 g/dl: 44.3% vs. 3.8–4.1 g/dl: 38.0% vs. >4.1 g/dl: 22.9%; log-rank p < 0.0001). After adjusting for established cardiovascular risk factors including age, acute coronary syndrome, BMI and CKD, serum albumin levels were significantly associated with incidence of MACE (HR 1.74 per 1-g/dl decrease, 95% CI 1.34–2.26, p < 0.0001) and all-cause mortality (HR 1.74, 95% CI 1.30–2.33, p = 0.0002). Pre-PCI low serum albumin level was associated with worse long-term outcomes, independent of traditional risk factors. Assessing albumin levels may allow risk stratification in patients with CAD undergoing PCI.