Our aim was to evaluate the clinical significance of the negative-balance isolated pelvic perfusion (NIPP) method using ultrahigh-dose cisplatin (CDDP) for ten cases of invasive bladder cancer with poor risk such as high-grade cancer, advanced clinical stage, or appearance of hydronephrosis. A CDDP dosage of 200–300 mg/body was used under the NIPP method. To confirm safety and efficacy, peripheral blood, pelvic arterial blood, pelvic venous blood, and urine were collected for sampling of the platinum (Pt) concentrations. These samples were investigated and compared with those following previous intraarterial chemotherapy sessions. The Pt concentrations in pelvic blood under intraarterial chemotherapy and NIPP were 5.97 ± 2.06 and 24.15 ± 4.61 μg/ml, respectively. By contrast, the Pt concentration in peripheral blood under NIPP was half the level under conventional intraarterial chemotherapy. No severe adverse events were found in terms of gastrointestinal and hematological toxicity, but renal function was impaired in some cases. Pathological or surgical complete response (CR) was achieved in five of ten cases (50%) in spite of the group being poor risk, and bladder preservation was possible in all the CR cases. Patients with CR experienced survival in all terms of observation. The NIPP method was able to deliver high levels of CDDP concentration in pelvis cavity without severe adverse events. The NIPP method makes it possible to achieve CR for the patients with invasive bladder cancer with poor risk who rejected cystectomy.