Purpose: Endocrine dysfunctions such as impaired growth, delayed puberty, and low bone mineral density have been reported in children and adolescents with inflammatory bowel disease (IBD). This study was performed to investigate the frequency, clinical characteristics, and outcomes of endocrine manifestations of IBD in children and adolescents. Methods: This study included 130 patients with IBD (120 with Crohn disease [CD] and 10 with ulcerative colitis [UC]) diagnosed before 18 years of age. Growth profiles, pubertal status, 25-dihydroxyvitamin D3 [25(OH)D3] levels, and bone mineral densities (BMD) were reviewed retrospectively. Disease activity indices were evaluated as a pediatric CD activity index ( PCDAI) score. Results: The mean age at diagnosis of CD and UC were 13.4 ± 2.5 years and 12.8 ± 4.5 years, respectively. Short stature was found in 11 patients (8.5%). As the PCDAI scores of CD patients increased, weight, serum IGF-1 and IGFBP-3 SDSs were significantly decreased (weight and serum IGF-1 SDS; P 0.001, serum IGFBP-3 SDS; P = 0.022). During the follow-up period, height and weight SDSs were not significantly improved ( P = 0.499 and P = 0.520, respectively). Among 109 patients with pubertal age, delayed puberty was found in 11 patients with CD (10.1%). Serum testosterone levels were significantly decreased in accordance with high PCDAI scores of CD patients ( P = 0.026). However, LH, FSH, and estradiol levels were not associated with disease activity ( P ＞ 0.05). Vitamin D deficiency and osteoporosis were documented in 83.8% and 33.1%, respectively. As the PCDAI scores of CD patients increased, 25(OH)D3 levels were significantly decreased ( P = 0.018). There was no significant correlation between 25(OH)D3 levels and osteoporosis ( P = 0.888). Conclusions: Vitamin D deficiency was frequently found in pediatric IBD patients. As the disease activity become severe, parameters for growth, sexual development, and vitamin D status were aggravated. Therefore, early interventions and nutritional support are essential to prevent endocrine manifestations and maintaining disease remission in pediatric patients with IBD.