Objective: To investigate the clinical and genetic characteristics of congenital isolated adrenocorticotropic hormone (ACTH) deficiency. Methods: The clinical and laboratory characteristics of 5 cases with congenital isolated ACTH deficiency diagnosed in the Department of Endocrinology of the Children's Hospital, Capital Institute of Pediatrics from January 2019 to March 2021 were retrospectively analyzed. The general conditions, clinical manifestations, laboratory examinations, genetic charcteistics, treatment and follow-up (up to October 2021) were analyzed. Results: Of the 5 cases, 1 was female and 4 were males, aged from 13 months to 6 years at the time of consultation. The symptoms of hypoglycemia and convulsion were presented in infancy, and 4 cases had infantile cholestasis. Glucose level of 5 cases ranged from 0.79-2.20 mmol/L, ACTH ranged from <1.00-4.17 ng/L, and cortisol ranged from 0.2-3.8 μg/L. Whole exon sequencing revealed that 3 cases carried homozygous TBX19 variations, and 2 cases had compound heterozygous TBX19 variations, including 3 variants that had been reported before and 3 novel variants were found. After the diagnosis was confirmed, all the cases were treated with hydrocortisone. Hypoglycemia was all corrected during the follow-up, and 4 cases no longer had convulsions. Conclusion: Congenital isolated ACTH deficiency should be considered in neonates and infants with cholestasis and hypoglycemia, and the diagnosis can be confirmed by genetic testing.