Central precocious puberty (CPP) may be the first presentation of nonclassical congenital adrenal hyperplasia (NCCAH) in girls. Data on the prevalence and the clinical phenotype of CPP associated with NCCAH are sparse. Objectives: To study the clinical and laboratory characteristics that could differentiate idiopathic CPP from CPP associated with NCCAH and to determine the prevalence of NCCAH among girls with CPP. Design: Case-control study. Setting: Tertiary pediatric endocrinology institute. Participants and Methods: From 2008 to 2017, 147 girls who had undergone stimulation tests with gonadotropin-releasing hormone and ACTH were diagnosed with CPP; of these, seven (4.8%) were eventually diagnosed with NCCAH. These seven patients together with 30 girls who presented with CPP during 1984 to 2008 and were later diagnosed with NCCAH comprised the NCCAH group. Demographic, anthropometric, clinical, and laboratory data were compared between the NCCAH group and the 140 girls with idiopathic CPP (ICPP group).