Background: TAR-200 is a novel intravesical drug delivery system designed to provide a continuous, slow release of gemcitabine within the bladder. Prolonged gemcitabine exposure over days, instead of hours, such as with current standard intravesical installations, may achieve more efficient and effective tumor response. We report on the safety and tolerability of TAR-200 in patients with non-muscle–invasive bladder cancer (NMIBC). Methods: In this phase 1b, open-label, prospective study, patients with a papillary recurrence after prior histologically proven, intermediate risk (IR)-NMIBC received two 1-week TAR-200 dosing cycles over a 4- to 6-week period. The study used a marker lesion/ablation design. Cystoscopy was performed to assess for recurrent papillary disease and for complete transurethral resection of the residual bladder tumor. The primary outcome was safety of TAR-200. Secondary outcomes were tolerability, pharmacokinetics, preliminary efficacy, and immunohistochemistry. Results: In total, 12 patients received TAR-200 treatment. Insertion and removal of TAR-200 was uneventful. No TAR-200-related serious adverse events (AEs) occurred. Four patients had no TAR-200-associated AEs; the remainder had varying degrees of AEs (all grade ≤2 [CTCAEv4.0]), mainly consisting of low-grade urinary urgency, urinary frequency, and dysuria, with no delay in the treatment schedule. Two patients refused a second dosing cycle due to urinary urgency and frequency. Plasma gemcitabine concentrations remained below the lower limit of detection. Five of 12 patients (42%) had complete response (CR); of these, 4 had a pathologic CR and 1 had CR based on visual assessment (with no biopsy available for pathologic assessment). Conclusions: In this small, phase 1 series, TAR-200 appears to be safe and well tolerated in patients with IR-NMIBC. Clinical trial information: NCT02720367.