The recurrence rate following endoscopic treatment of non-muscle-invasive bladder cancer (NMIBC) remains high. Standard treatment includes intravesical instillation of chemotoxic agents such as mitomycin C (MMC) to reduce recurrence. It is postulated that upfront administration of hyperthermic intravesical MMC (HIVEC) immediately after transurethral resection of bladder tumour (TURBT) may enhance its efficacy, but evidence from human trials is scant. This pilot study explored the safety of immediate intravesical MMC instillation following TURBT using a conductive HIVEC system (Combat BRS). Patients diagnosed with papillary bladder tumours scheduled for TURBT were recruited. Among 29 patients treated with HIVEC, there was minimal additional postoperative morbidity. The majority (79.3%) were discharged after a hospital stay of 1 d, and no patient required bladder irrigation. There were six grade I-II adverse events (20.7%) and one grade III event (3.4%). No recurrences were observed within 3 mo, and the 12-mo recurrence rate was 4.5%. The study findings demonstrate that immediate HIVEC MMC instillation following TURBT is safe. Further research is needed to assess long-term efficacy in comparison to standard cold MMC. PATIENT SUMMARY: Non-muscle-invasive bladder cancer is treated with tumour removal via a telescope inserted into the bladder through the urethra (called TURBT). We tested the safety of treating the bladder with a warm solution of a chemotherapy drug (mitomycin C) immediately after TURBT, as this may prevent tumour recurrence. The treatment was safe and well tolerated. Further trials are needed with more patients and longer follow-up to confirm the results.