Monocyte chemotactic protein-1 (MCP-1), also known as "chemokine ligand 2" (CCL2), is a monocyte-attracting chemokine produced in lung epithelial cells. We previously reported an association of increased levels of plasma MCP-1 with primary graft dysfunction (PGD) after lung transplantation in a nested case-control study of extreme phenotypes using a multiplex platform. In this study, we sought to evaluate the role of plasma MCP-1 level as a biomarker across the full spectrum of PGD. We performed a prospective cohort study of 108 lung transplant recipients within the Lung Transplant Outcomes Group cohort. Plasma MCP-1 levels were measured pretransplantation and 6 and 24 hours after transplantation. The primary outcome was development of grade 3 PGD within 72 hours of transplant, with secondary analyses at the 72-hour time point. Multivariable logistic regression was used to evaluate confounding. Thirty subjects (28%) developed PGD. Median MCP-1 measured at 24 hours post-transplant was elevated in subjects with PGD (167.95 vs 103.5 pg/mL, P = .04). MCP-1 levels at 24 hours were associated with increased odds of grade 3 PGD after lung transplantation (odds ratio for each 100 pg/mL, 1.24; 95% confidence interval, 1.00-1.53) and with grade 3 PGD present at the 72-hour time point (odds ratio for each 100 pg/mL, 1.57; 95% confidence interval, 1.18-2.08), independent of confounding variables in multivariable analyses. MCP-1 levels measured preoperatively and 6 hours after transplant were not significantly associated with PGD. Persistent elevations in MCP-1 levels at 24 hours are a biomarker of grade 3 PGD post-transplantation. Monocyte chemotaxis may play a role in the pathogenesis of PGD.