Background: Adnexal mass means any swelling arising from the adnexa which comprises the ovary, fallopian tube, structures in broad ligaments, and other connective tissues in parametrium. Adnexal mass can be an incidental diagnosis, or it may be associated with other symptoms like pain in the abdomen. It is very commonly encountered in our clinical practice. Materials and methods: A single-center prospective observational study involving 60 adolescent girls who came to the OPD or emergency in Lokmanya Tilak Municipal Medical College and Hospital with clinical or radiological findings s/o adnexal mass from the year 2017 to 2019 over a period of 20 months. Results: The maximum number of adnexal masses belonged to the age-group of 14–16 years (56.7%). About 60% of patients had pain in the abdomen. While only 36.7% of patients had regular menses, and 3.3% had not attained menarche. The most common associated complaint was dysmenorrhea (20%) followed by menorrhagia (13.3%). In 86.7% of patients, no mass was palpable per abdomen, while 6.7% had a mass of 12 weeks palpable per abdomen and 6.6% had a mass of more than 12 weeks palpable per abdomen. Almost 35% of patients when followed up, showed a decrease in the size of the mass, while in 6.8% the size of the mass increased. Bilaterality was found in 10% of cases while left-sided masses (48.3%) were seen more commonly than those on the right side (41.7%). In total, 53 masses (88.3%) were non-neoplastic and 7 (11.7%) masses were neoplastic, of which 10% were dermoid and 1.7% were dysgerminoma. In our study, 8.5% of patients had ovarian torsion. Cancer Antigen 125 (CA-125) was raised in around 18.3% of patients. Out of 60 patients, 68.3% were managed conservatively out of which 3.3% underwent medical management, 28.3% underwent laparoscopy, and 3.3% patients underwent laparotomy. Conclusion: Adnexal masses are common among adolescents, they are usually benign and often can be managed expectantly. The evaluation of adolescents with an adnexal mass should include menstrual history and a confidential inquiry regarding sexual activity. Among benign lesions, a simple cyst is the most common pathology of adnexal mass. Germ-cell tumors are the most common ovarian malignancies in children and adolescents. Management of adnexal masses in adolescents should prioritize ovarian conservation to preserve fertility.