Prevention of chronic kidney allograft injury (CAI) is a major goal in improving kidney allograft survival; however, the mechanisms of CAI are not clearly understood. The current study investigated whether alternatively activated M2-type macrophages are involved in the development of CAI. A retrospective study examined kidney allograft protocol biopsies (at 1 h and at years 1, 5, and 10—a total of 41 biopsies) obtained from 13 children undergoing transplantation between 1991 and 2008 who were diagnosed with CAI: interstitial fibrosis and tubular atrophy (IF/TA) not otherwise specified (IF/TA-NOS). Immunostaining identified a significant increase in interstitial fibrosis with accumulation of CD68 + CD163+ M2-type macrophages. CD163+ cells were frequently localized to areas of interstitial fibrosis exhibiting collagen I deposition and accumulation of α-smooth muscle actin (SMA) + myofibroblasts. There was a significant correlation between interstitial CD163+ cells and the parameters of interstitial fibrosis (p