Peripheral artery disease (PAD) is a risk factor for the development of heart failure and mortality. The serum levels of carboxy-terminal telopeptide of type I collagen (I-CTP), a marker for collagen degradation derived from the extracellular matrix of vascular and myocardial tissue, is reportedly a useful marker for cardiac events in patients with heart disease. However, it remains unclear whether I-CTP can predict poor clinical outcome in patients with PAD. Serum I-CTP was measured in 246 consecutive PAD patients who underwent endovascular therapy. Patients were prospectively followed during a median follow-up period of 887 days with the end points of major adverse cardiovascular events (MACE). I-CTP was significantly higher in patients with critical limb ischemia than those without. A multivariate Cox proportional hazard analysis revealed that I-CTP was an independent predictor of MACE after adjusting for confounding factors. Patients were stratified into three groups based on I-CTP level tertile, and those with third tertile had higher levels of brain natriuretic peptide levels and high-sensitivity C-reactive protein compared to the other two groups. Kaplan–Meier analysis demonstrated that patients in the highest tertile of I-CTP also had the greatest risk of MACE. The net reclassification index significantly improved with the addition of I-CTP to basic predictors. I-CTP is a reliable marker and indicator for MACE in patients with PAD.