Background: Scheuermann’s disease is the most common cause of hyperkyphosis of the thoracic spine during the adolescence period. It causes neck and lower back pain, restriction of lung expansion, traction of the spinal cord, increased vulnerability to vertebral fracture, and a hump. Patients with curves < 60° are treated conservatively, while surgery is used for patients with curves > 60°. The purpose of this prospective cohort study was to assess the quality of life and functional changes in conservatively or surgically treated Scheuermann’s disease patients with a curve size of 50°–65° in north Jordan. Methods: Sixty-three adolescent patients with Scheuermann’s kyphosis (aged between 10 and 18 years) were treated at our hospital between January 2014 and August 2018. All patients were investigated clinically, radiologically (Cobb’s angle), and functionally (Oswestry Disability Index [ODI], Scoliosis Research Society 22 revision [SRS-22r] questionnaire, and pulmonary function test [PFT]) preand post-treatment (final follow-up). Patients were randomly selected for treatment method (conservative versus surgical). Results: There were 31 patients (mean age, 15.48 ± 2.50 years) and 32 patients (mean age, 16.19 ± 1.51 years) treated conservatively and surgically, respectively. Mean ± standard deviation of ODI, SRS-22r, and Cobb’s angle of the surgical group improved from 16.8% ± 14.3%, 3.5 ± 0.5, and 58.75° ± 3.59°, respectively, pre-surgery to 13.4% ± 10.8%, 4.2 ± 0.5, and 41.53° ± 3.94°, respectively, post-surgery, while those of the conservative group became worse from 12.6% ± 13.4%, 3.9 ± 0.7, and 56.1° ± 3.3°, respectively, to 20.1% ± 13.6%, 3.5 ± 0.7, and 58.8° ± 5.8°, respectively. The surgical group showed better improvement in all scores than the conservative group (p < 0.05), as well as in PFT. Conclusions Surgical treatment of Scheuermann’s kyphosis with curves of 50°–65° resulted in better QOL, Cobb’s angle, and PFT than conservative treatment. This was because of lower patient cooperation in the conservative management group, which made the curve less flexible for exercises and bracing.