Abstract Objective: To explore the potential role of M1-polarized macrophages in the pathogenesis of endothelial-to-mesenchymal transition (endothelium-to-myofibroblast transition, EndMT) and chronic allograft dysfunction (chronic allograft dysfunction, CAD). Methods: The GSE21374 transcriptome array from GEO public database was downloaded, and cibersort software was used to examine immune cell infiltration status in allograft tissues of CAD patients. Then the allograft tissues were collected from patients diagnosed with CAD in our center. Immunofluorescence, polymerase chain reaction (PCR) and western blotting (WB) were used to observe infiltration of M1-polarized macrophages. Finally, we used lipopolysaccharide and interferon-γ to induce the polarization of Raw264.7 macrophage cell line into M1 macrophages in vitro. A trans-well chamber was used to establish a co-culture system for the M1 macrophages and balb/c mouse-derived aortic endothelial cells. PCR and WB assays, as well as cell immunofluorescence, were performed to examine the expression of CD31 and α-SMA(alpha-SMA). Results: Based on the public database, monocytes and macrophages were observed to be highly expressed in allograft tissues from CAD patients (P < 0.05). Similarly, significant infiltration of CD68 (+) iNOS (+) M1 macrophages in glomerulus and interstitial area of allograft with CAD in our center was reported, and PCR results showed that surface marker of M1 macrophages iNOS (inducible nitric oxide synthase) was increased significantly compared to the normal kidney tissues. Co-cultured with M1 macrophages, the expression of VE-cadherin protein and mRNA were remarkably reduced, along with the increased expression of α-SMA，vimentin，and collagen I proteins. Conclusion: We have observed significant M1 macrophages infiltration in the allograft tissues diagnosed with CAD, which may induce the occurrence of EndMT and CAD progression in renal transplant recipients.