Karyomegalic interstitial nephritis (KIN) is a rare disease entity that was first described by Burry in 1974. The prevalence of this disease is less than 1% and its pathogenesis is unclear. KIN is characterized by chronic tubulointerstitial nephritis associated with enlarged tubular epithelial cell nuclei, which leads to progressive decline of renal function. The disease has no known treatment. Here, we report on a 50-year-old female patient who presented with asymptomatic progressive decline of renal function. Renal biopsy demonstrated chronic tubulointerstitial nephritis with markedly enlarged and hyperchromic nuclei of tubule epithelial cells the hallmark of karyomegalic nephritis. Clinical and pathologic findings of this case are discussed in light of the available literature.