Herein, we present the clinical and genetic features of a 1-year-old Chinese child diagnosed MODY9 with a novel heterozygous c.487C>T mutation in the PAX4 gene and further discuss the relevant literature to raise clinicians’ awareness of this disease and suggest approaches to precisely diagnose and manage MODY9. The gene discussed is PAX4; the disease is maturity-onset diabetes of the young type 9.