It is unclear how age affects rates and causes of unplanned early readmissions after percutaneous coronary intervention (PCI). We analyzed patients in the Nationwide Readmission Database in the United States from 2010 to 2014 and examined the impact of age on readmissions after PCI. The primary outcomes were age-specific 30-day rates and causes of unplanned readmissions. A total of 2,294,345 procedures were analyzed with a 9.6% unplanned readmission rate within 30 days. Unplanned readmissions were 8.1%, 8.1%, 9.5%, and 12.6% for age groups <55, 55.0 to 64.9, 65.0–74.9, and ≥75 years, respectively. With increasing age, there was an increase in the rate of noncardiac causes for readmissions (for ages <55, 55.0 to 64.9, and ≥75 years, the rates were 54.1%, 54.8%, 56.6%, and 57.1%, respectively; p <0.001). Older age was associated with an increased prevalence of infections (13.9% ≥75 years vs 7.7% <55 years), gastrointestinal disease (11.5% ≥75 years vs 9.5% <55 years), and bleeding (7.4% ≥75 years vs 2.9% <55 years) as causes for noncardiac readmissions and a reduced prevalence of nonspecific chest pain (9.9% ≥75 years vs 31.4% <55 years). For cardiac causes, older age was associated with increased prevalence for readmissions due to heart failure (34.6% ≥75 years vs 11.9% <55 years) but a reduced prevalence of coronary artery disease, including angina (25.7% ≥75 years vs 51.3% <55 years). In conclusion, older patients have the highest rates of unplanned 30-day readmissions after PCI, with different causes for readmission compared with younger patients. Interventions designed to reduce readmissions after PCI should be age specific.