A solitary fibrous tumor (SFT) is a rare spindle cell neoplasm that arises most commonly in the pleura but has recently been described in various extrapleural sites. SFTs occurring in the renal pelvis or peripelvis are extremely rare, and only 3 cases have been reported. We report here on a 71-year-old woman who presented with an incidentally detected left renal mass and underwent radical nephroureterectomy under the suspicion of renal pelvis cancer. The pathological examination of the tumor revealed a SFT occurring in the renal peripelvis. The patient has no evidence of disease 1 year after the surgery. Most SFTs appear to pursue a benign course, although, because some of them have the potential to recur or metastasize, careful long-term follow-up is necessary.