Cardiac allograft vasculopathy (CAV) remains a major cause of morbidity and mortality among long-term heart transplant recipients. There is an unmet need for a non-invasive biomarker of CAV that could obviate the need to perform surveillance coronary angiograms in these patients. Our aim was to evaluate the performance of Donor-derived Cell Free DNA (dd-cfDNA) as a biomarker of CAV. We prospectively measured dd-cfDNA levels in all patients undergoing routine coronary angiography >1 year after heart transplant at a single center. Endpoints included the association between dd-cfDNA levels and the presence CAV, according to several prespecified criteria. We included 94 heart transplant recipients, a median of 10.9 years after transplant. Coronary angiogram revealed CAV , CAV , CAV , and CAV in 61, 19, 14, and 6% of patients, respectively. Comparison of dd-cfDNA levels in patients with CAV and CAV (primary end-point) did not show significant differences (0.92%, IQR 0.46-2.0 vs. 0.46%, IQR 0.075-1.5, = 0.059), nor did the comparison between patients with stable CAV (no new coronary lesions since previous angiogram, = 77) and progressive CAV ( = 17); dd-cfDNA values 0.735% (IQR 0.195-2.0) vs. 0.9% (IQR 0.12-1.8), = 0.76. However, we found an association between NTproBNP levels and CAV degree ( = 0.017). Dd-cfDNA levels did not correlate with NTproBNP (ρ = -0.095). In this study, dd-cfDNA did not perform as a useful biomarker to avoid surveillance coronary angiograms for CAV diagnosis. Potential Role of Donor-derived Cell Free DNA as a Biomarker in Cardiac Allograft Vasculopathy, NCT04791852.