Menstrual disturbances are common among adolescents with a prevalence rate of 11.3–26.7%. The most frequent menstrual irregularities are oligomenorrhea, menorrhagia, polymenorrhoea, and hypomenorrhea. PCOS (polycystic ovarian syndrome) is now recognized as the most prevalent endocrine disorder among the women of reproductive age. The current study was planned to evaluate socio-demographic factors, endocrine profiles, and ovarian morphology among adolescent girls with menstrual irregularities and compare these parameters in different phenotypes of adolescent PCOS cases. It is a hospital-based cross-sectional study among 248 adolescent girls (10–19 years) with menstrual irregularities. After obtaining informed consent, history and clinical examination findings were recorded on preform proforma. All girls were assessed on day 2/3 of the menstrual cycle for hormonal profile (serum TSH, FSH, LH, prolactin, and serum testosterone) and ovarian morphology (by transabdominal ultrasonography). All participating girls were divided into three groups (groups 1, 2, and 3) corresponding to phenotypes A, B, & D as per the Rotterdam criteria. In the study, oligomenorrhea was the most common menstrual disorder (70.97%). Biochemical hyperandrogenism and thyroid dysfunction were reported in 14.91% and 8.46% of girls, respectively. Our study noted that phenotype D ,i.e., group 3 (MI + PCOM-HA; 49.43%) was the most common phenotype in the study. In a comparative analysis of different groups, significant differences ( p < 0.05 ) in hormonal and metabolic parameters showed highest in group 2, which represents phenotype B of PCOS (hyperandrogenic anovulation). This analysis revealed that adolescent hyperandrogenism (phenotypes A and B) is associated with a more deranged hormonal and metabolic profile than nonandrogenic PCOS (phenotype D). To prevent long-term sequelae, lifestyle changes, early treatment, and close follow-up are recommended in this subset of girls.