Solitary kidney is congenital or acquired, and the main cause of the latter includes nephrectomy. Regardless of the causes, individuals with a solitary kidney may have renal dysfunction. However, limited data on antineoplastic effects on renal function are available in chemotherapy for head and neck cancer. In this report, we describe a case of a solitary kidney patient with mandibular gingival cancer who was treated with induction chemotherapy and surgery. A 55-year-old Japanese woman was referred to us with a persistent pain in the left mandible that lasted for a few months. Her medical history included right nephrectomy after a traffic accident in childhood. An incisional biopsy revealed well-differentiated squamous cell carcinoma. The patient was diagnosed with stage G3a chronic kidney disease. She underwent two cycles of induction chemotherapy with docetaxel, cisplatin, and 5-fluorouracil. The cisplatin dose was reduced by 25%, but the docetaxel and 5-fluorouracil doses were not reduced. In both cycles, eGFR decreased, and serum creatinine transiently increased on Day 12; however, her renal function was restored at the end of each cycle. Then she underwent left mandibulectomy, buccal mucosa and partial maxillectomy, reconstructive surgery with a submental island flap. No infiltrative squamous cell carcinoma, sign of recurrence and aggravation of kidney function were observed. This suggested that, in patients with a solitary kidney, reduced cisplatin dose can show the favorable antineoplastic effect, maintaining renal function in the short term.