Few studies were performed to evaluate the prevalence of latent autoimmune diabetes in adults (LADA) and the difference of chronic complications between LADA, T1DM, and T2DM in Korean. The aim of this study is to establish the prevalence of LADA in a diabetic clinic of Soonchunhyang University hospital and to compare the phenotypic characteristics according to DM classification based on positivity of glutamic acid decarboxylase antibodies (GADA). Also, another important point concerns the occurrence of diabetes chronic microvascular complications in LADA. 323 patients who were checked GADA among diabetic patients admitted at Soonchunhyang University hospital were recruited. Twenty-eight patients (8.7%) were identified as positive for GADA. 11.5% (n = 37) were diagnosed with T1DM and 5.3% (n = 17) were diagnosed with LADA. GADA titer showed significant negative correlation with age of onset, total cholesterol (TC), triglyceride (TG), fasting C-peptide, stimulated C-peptide, BMI, and positive correlation with HbA1C and HDL-C. Compared with those that tested negative for GADA, patients with GADA positive had lower values of onset age, BMI, TC, TG, LDL-C, fasting, and stimulated C-peptide levels and higher values of HbA1C. A significant gradual increase of values was observed for the onset age, BMI, SBP, DBP, fasting, and stimulated C-peptide across the T1DM, LADA, and T2DM subgroups. Concerning the chronic complications there was no difference in prevalence of retinopathy, neuropathy and nephropathy between three groups. Of LADA patients, 12 patients were receiving insulin treatment and mean time to insulin initiation was about 37 months. In conclusion, because our study suggests LADA subgroups in Korea appear to have a faster decline in C-peptide levels, it is worth detecting the patients with LADA early and effort to preserve beta cell function. Furthermore, our results showed that the prevalence of microvascular complication was comparable between the subgroups.