Unicameral bone cysts (UBC) are benign, fluid-filled cavitary lesions that predominantly affect the metaphyseal region of long bones in children and adolescents, with the proximal humerus being the most common site after the proximal femur. These cysts pose significant clinical challenges due to their propensity to cause pathological fractures, which can lead to functional impairment and growth disturbances if not managed appropriately. This case study presents a comprehensive analysis of a 12-year-old male patient who sustained a pathological fracture through a unicameral bone cyst located at the proximal-middle third junction of the right humerus following minor trauma during sports activity. The patient presented with acute onset of severe arm pain, swelling, and inability to move the affected limb after falling during a basketball game. Clinical examination revealed localized tenderness, deformity, and restricted range of motion at the shoulder and elbow joints. Radiological investigations including plain radiographs and magnetic resonance imaging confirmed the presence of a large unicameral bone cyst with associated pathological fracture and revealed characteristic features including a centrally located, well-defined, fluid-filled cavity with thin cortical walls and absence of internal septations. The patient underwent surgical management consisting of open reduction and internal fixation with a locking compression plate, followed by cyst curettage, bone grafting using autologous iliac crest bone graft, and injection of bone marrow aspirate concentrate to promote healing and prevent recurrence. Post-operative recovery was uneventful with progressive improvement in pain, range of motion, and functional outcomes over a 12-month follow-up period. Serial radiographs demonstrated excellent fracture healing, significant cyst resolution, and restoration of normal bone architecture without evidence of recurrence. This case highlights the importance of early recognition, appropriate imaging, and timely surgical intervention in managing unicameral bone cysts with pathological fractures, emphasizing the need for a multidisciplinary approach involving orthopedic surgeons, pediatric specialists, and rehabilitation teams to optimize patient outcomes and prevent long-term complications.