Background: The prevalence of childhood obesity is in creasingly worldwide. Abnormal glucose metabolism (ASM) including impaired fasting glucose (IFG), impaired glucose tolerance (IGT) and type 2 diabetes (T2DM) is a common endocrine complication among overweight and obese children and adolescents. Few studies of AGM are available in Thailand.Objectives: The study aimed to establish the prevalence of AGM and identify associated complications among overweight and obese children and adolescents.Methods: Data of overweight and obese children and adolescents, aged 6 to 18 years, undergoing oral glucose tolerance test (OGTT) at phramongkutklao Hospital were reviewed retrospectively. Fasting blood sugar, Hemoglobin Ale (HbA1c). fasting insulin, triglyceride, high-density lipoprotein, low-density lipoprotein, aspartate transaminase and alanine aminotransferase were derived from fasting measurement. Homeostatic model assessment was calculated to represent the insulin resistance.Result: A total of 204 children and adolescents (122 males) were included. Mean age was 12.1 ± 2.6 years and percent weight for height was 168.8 ± 25.4% The overall prevalence of AGM was 20.6%, 1 % had T2DM, 0.5% had IFG, 36% had IGT and 1.5% had combined IFG/IGT. Among the AGM, IGT was the most frequent subtype representing 92.8% (39/42 cases) but only 2 cases of T2DM were diagnosed in our study. The AGM group had significantly higher FPG (p=0.034), HbA1c (p=0.006) and cholesterol levels (p=0.043) than those of the nonabnormal glucose metabolism (NGM) groupConclusion: Prevalences of AGM among overweight and obese children and adolescents were high. IGT was the most frequent group.