To analyze the genetic and clinical characteristics, treatment and prognosis of patients diagnosed with maturity onset of diabetes of the young (MODY) 12 subtype. This retrospective study collected and analyzed data from 5 children with MODY12 subtype caused by ABCC8 gene variants who underwent inpatient and outpatient genetic testing at Beijing Children's Hospital from January 2016 to December 2023. Their clinical and genetic features, treatment, and follow-up results were analyzed. Among the 5 patients with MODY12 subtype, 4 were male and 1 was female, with an age of 13.4 (5.5, 14.6) years. Four of the patients were born large for gestational age, while one was born small for gestational age. Two patients were overweight or obese. Three patients exhibited typical symptoms of diabetes, while 2 were incidentally found to have elevated blood glucose level. One patient was found to have diabetic ketoacidosis at onset, who was diagnosed with congenital hyperinsulinism during the neonatal period and received diazoxide treatment, and experienced intellectual developmental delay. All 5 patients had autosomal dominant inherited diabetes within 3 generations. The fasting blood glucose at onset was 7.5 (6.5, 10.0) mmol/L, the haemoglobin A1c (HbA1c) was 11.8% (7.5%, 13.5%), and the fasting C-peptide was 1.2 (1.1, 2.2) μg/L. The duration of follow-up was 15 (9, 32) months. One patient underwent lifestyle intervention, 2 received metformin orally, 1 received insulin therapy, and the other received subcutaneous injection of insulin combined with sulfonylurea orally. At the last follow-up, the median fasting blood glucose was 6.1 (5.1, 7.0) mmol/L, the HbA1c was 5.9% (5.7%, 7.1%), and the fasting C-peptide was 1.7 (0.9, 2.9) μg/L. One patient developed diabetic retinopathy. There were 4 missense variations in ABCC8 gene and one in-frame deletion, all of which were maternally inherited heterozygotes. MODY12 subtype is a heterogeneous disorder with the age of onset from infancy to adolescence. It can present as mild hyperglycemia or diabetic ketoacidosis, and has a high incidence of obesity. Definitive diagnosis can be achieved through genetic test, and individualized treatment is recommended based on glucose levels.