Background/Objectives: Scoliosis is a prevalent comorbidity in Rett syndrome (RTT), often necessitating surgical intervention. This study investigated the impact of a 10-month individualized home exercise program (HEP) on scoliosis progression and gross motor function in girls aged six to 16 years with RTT. Methods: A multiple-baseline single-case design (AABA) was employed with 20 participants. A remotely supervised HEP, based on established principles focused on posture and physical activity, was implemented daily for at least one hour. The primary outcome was the rate of scoliosis progression assessed through the Cobb angle change measured via spinal radiographs at baseline, pre-intervention, and post-intervention. The secondary outcome was the gross motor function. Results: The HEP did not significantly reduce the rate of scoliosis progression. However, individual responses varied, with three participants showing scoliosis reduction. Significant improvements were observed in gross motor function, particularly in standing, walking, and stair-climbing abilities. Conclusions: The HEP did not significantly impact overall scoliosis progression, but a significant improvement was found in gross motor function. Further research into larger sample sizes is needed to confirm the effectiveness of exercise interventions in people with RTT.