Platinum-based antineoplastic drugs are widely used in the treatment of solid tumors. Carboplatin, a second generation platinum compound, was developed to have less nonhematologic toxicity, in comparison with cisplatin. We report on a 34-year-old woman with breast cancer who developed gross hematuria after initiation of carboplatin-based chemotherapy. To our knowledge, there are very few cases reports of carboplatin-associated gross hematuria.