Objectives Although new-born screening (NBS) for classical congenital adrenal hyperplasia (C-CAH) has been available for decades, it is not widely implemented. We assessed the usefulness of introducing NBS for C-CAH, by analyzing presenting status of infants with C-CAH, over the past two decades, in Sri Lanka. Methods This retrospective clinic-based study, from the largest tertiary children’s hospital in Sri Lanka, analyzed initial presenting features of children with C-CAH from 1999 to 2018, in the absence of NBS for CAH, and included gender-based comparisons. Results Features suggestive of impending adrenal-crisis were seen at initial presentation in >80 % (dehydration 70%, hyponatremia 65%, hyperkalemia 47%, vomiting 45%, hypoglycemia 22%, collapse 20%). Hyperpigmentation was seen in 78%, and consanguinity in 27%. There were fewer affected males (n = 12) compared to females (n = 28). Most girls (96%) had virilized genitalia, and 16 faced uncertainty about gender at birth. Median age at diagnosis was 20 days. More than 70% of children had SW-CAH (males = 9 and females = 20). There were fewer males with SW-CAH, and all had features of impending adrenal crisis, including severe hyponatremia in 50%, while 62% of girls also developed hyponatremia and 33% had hyperkalemia, prior to treatment. Treatment of SW-CAH was initiated at a median age of 30 days in boys, and 10 days of age in girls. Conclusion Many boys and girls with C-CAH from Sri Lanka presented late with impending adrenal crisis. Males were diagnosed later, and some possibly succumbed to C-CAH undiagnosed. These findings support including CAH in NBS programs to avert preventable childhood morbidity and mortality.