Background: Thoracic hyperkyphosis and impaired sagittal alignment may be associated with reduced thoracic mobility, altered movement strategies, discomfort, and poorer quality of life. Exercise programmes can improve postural parameters, but the additional value of real-time smartphone feedback during a three-dimensional corrective exercise programme remains insufficiently established. Objective: To compare an eight-week Schroth-based corrective exercise programme combined with smartphone-based real-time postural feedback with a dose-matched conventional postural exercise programme in middle-aged adults with increased thoracic kyphosis. Methods: This assessor-blinded, parallel-group randomized controlled trial model includes adults aged 40–60 years with increased thoracic kyphosis. Participants receive three 50-minute supervised sessions per week for eight weeks, plus 15 minutes of daily home practice. The primary outcome is thoracic kyphosis angle. Secondary outcomes include thoracic mobility, sagittal postural alignment, and quality of life. Assessments occur at baseline, week 4, week 8, and follow-up. Results: In the illustrative dataset, the combined Schroth and smartphone group shows larger numerical improvements in kyphosis, mobility, alignment, and quality of life than conventional postural exercise. These numerical findings are simulated and are not clinical evidence. Conclusion: The protocol provides a reproducible framework for testing whether immediate digital postural feedback adds benefit to a structured three-dimensional corrective exercise programme.