Abstract： Background::Maturity-onset diabetes of the young (MODY) is the most common monogenic diabetes. The aim of this study was to assess the prevalence of MODY in phenotypic type 2 diabetes (T2DM) among Chinese young adults.Methods::From April 2015 to October 2017, this cross-sectional study involved 2429 consecutive patients from 46 hospitals in China, newly diagnosed between 15 years and 45 years, with T2DM phenotype and negative for standardized glutamic acid decarboxylase antibody at the core laboratory. Sequencing using a custom monogenic diabetes gene panel was performed, and variants of 14 MODY genes were interpreted as per current guidelines.Results::The survey determined 18 patients having genetic variants causing MODY (6 HNF1A, 5 GCK, 3 HNF4A, 2 INS, 1 PDX1, and 1 PAX4). The prevalence of MODY was 0.74% (95% confidence interval [CI]: 0.40-1.08%). The clinical characteristics of MODY patients were not specific, 72.2% (13/18) of them were diagnosed after 35 years, 47.1% (8/17) had metabolic syndrome, and only 38.9% (7/18) had a family history of diabetes. No significant difference in manifestations except for hemoglobin A1c levels was found between MODY and non-MODY patients. Conclusion::The prevalence of MODY in young adults with phenotypic T2DM was 0.74%, among which HNF1A-, GCK-, and HNF4A-MODY were the most common subtypes. Clinical features played a limited role in the recognition of MODY.