The instillation of chemotherapeutic agents after transurethral resection of bladder tumor as an adjuvant treatment in bladder tumors is accepted as being safe if there is no associated bladder perforation. Mitomycin C (MMC) is a widely used agent for the adjuvant treatment of bladder tumors. A patient who developed MMC-induced bladder perforation and perivesical necrosis after an uneventful endoscopic tumor is presented. We suggest that the possible reason for such a complication could be deep resection at the anterior bladder wall. The treatment of the situation continued for an extended period, causing serious discomfort for the patient. Withholding immediate intravesical MMC instillation after resection of tumors on the anterior bladder wall ought to be considered in the early postoperative hours.