A 12 Year old boy, a case of ESRD due to nephronophthisis, 6 months after starting hemodialysis received kidney graft from a 16 years old cadaver. He had an uneventful transplantation course, on triple immunosuppressive regimen (MMF, Cyclosporine and Prednisolone) for 18 months with normal renal function when he developed generalized edema, hypertension, nephrotic range proteinuria, hyperlipidemia, hypoalbuminemia, and rise in BUN and creatinine. He had an enlarged and tender graft with increased parenchymal echogenicity and resistive index. At first clinical diagnosis of de novo glomerulonephritis was made but kidney biopsy was in favor of focal glomerulosclerosis and BK virus infection. Reduction of immunosuppressive dose and IVIG administration was ineffective and he became dialysis dependent. Gradual loss of renal function is a usual manifestation of BK virus nephropathy, but the combination that was described is not seen in the literature.