Lung transplantation is a therapeutic modality frequently utilized in end-stage lung disease. Unfortunately, lung transplant recipients have poor clinical outcomes, often due to the development of chronic rejection in the transplanted allograft. This process is characterized by neutrophil influx and extracellular matrix remodeling leading to luminal obstruction and airway inflammation. The molecular mechanisms underlying chronic rejection are poorly understood and disease-specific biomarkers are lacking. We report that in addition to increased levels of interleukin-8 (IL-8), the level of neutrophil chemoattractant proline-glycine-proline (PGP) is elevated in chronic rejection patient bronchoalveolar lavage (BAL) fluid and correlates with loss of lung function. The enzymes responsible for generating PGP, matrix metalloproteases-8 and -9 (MMP-8, -9) and prolyl endopeptidase (PE), are also elevated in chronic rejection samples. Together, IL-8 and PGP account for most of the neutrophil chemoattractant capacity seen in chronic rejection BAL fluid. Using specific neutralizing antibodies to both IL-8 and PGP, we demonstrate that PGP is the major neutrophil chemoattractant found in BAL fluid from individuals at the time of chronic rejection. These findings highlight the influence of a matrix-derived neutrophil chemoattractant in post-transplantation organ rejection and provide opportunities for the development of unique diagnostics and therapeutics to potentially improve disease outcomes.