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Background There is little evidence about whether mammalian target of rapamycin (mTOR) inhibitor could prevent post–kidney transplant (KT) urothelial carcinoma (UC) or not. The aim of this study is to analyze the role of mTOR inhibitor add-on in tacrolimus-based kidney transplant recipients. Method The data were obtained from the Kaohsiung Chang Gung Memorial Hospital using the Chang Gung Research Database and retrospectively reviewed from January 2000 to December 2015. Patients then were categorized into 2 groups: group FK (more than 2-year tacrolimus [FK] prescription) and group FK + mTOR inhibitor (more than 2-year tacrolimus plus at least 6-month continued sirolimus prescription). The primary end point is post-KT UC development. The secondary end point is mTOR inhibitor add-on effect on renal function deterioration episode. Results There were 140 patients with tacrolimus-based immunosuppressant (group FK) and 82 patients with tacrolimus-based and add-on mTOR inhibitor regimen (group FK + mTOR inhibitor). The follow-up duration, sex distribution, and combined mycophenolate mofetil rate are similar in both groups. Younger age, lower tacrolimus trough level, lower UC incidence, and longer KT-to-UC interval were observed. Short- to intermediate-term results revealed noninferior graft outcome by creatinine level or creatinine deterioration. Conclusions In our preliminary result, mTOR inhibitor add-on in patients with tacrolimus-based regimen revealed less post-KT UC occurrence. In addition, noninferior graft outcome was also observed. In Taiwan, a high UC prevalence area, mTOR inhibitor add-on strategy can be considered as a preventive strategy for UC after KT.