BACKGROUND Polyomavirus nephropathy (PVN) is a rare kidney disease caused by the BK virus, a strain of polyomavirus. The disease primarily affects transplant recipients, which is related to intensive immunosuppression protocol and can lead to kidney allograft failure. OBJECTIVE The objective of this study is to analyze histopathological features of PVN using the Banff 2018 PVN classification and to determine clinical features and outcomes of patients with PVN in each histologic class. METHODS The study included 44 patients who had been diagnosed with PVN by renal allograft biopsy in a large tertiary care hospital in Thailand from January 2011 to January 2020. The kidney biopsy slides were reviewed for Banff 2018 PVN classification and other histologic features. Patient demographic information, clinical data, and laboratory results were retrospectively collected. RESULTS Nine (20.45%), 27 (61.36%), and eight (18.18%) cases of PVN were Class I, Class II, and Class III, respectively. The time from transplant to PVN diagnosis for Classes I, II, and III was four, 19, and 33.5 months, respectively. Class III had the worst clinical outcomes in terms of deterioration of allograft function, the lowest rate of resolution, and the highest rate of graft failure. CONCLUSIONS PVN classification provides prognostic information in renal allograft biopsy. Our study confirmed the validity of the three-tier histologic PVN classification put forward by the Banff Working Group in 2018.