Purpose: This study compares the rehabilitation adherence, physical activity (PA) levels, and quality of life (QoL) of individuals with idiopathic scoliosis (IS) during and before the COVID-19 Pandemic. Methods: This study included 74 individuals with IS between the ages of 9 and 18 years. The Exercise Adherence Rating Scale (EARS) was used to assess adherence to exercise therapy protocols, the International Physical Activity Questionnaire Short Form (IPAQ) was used to evaluate PA levels, and the Scoliosis Research Society-22 Patient Questionnaire (SRS-22) was used to measure QoL. Results: Section B score of the EARS decreased (p=0.041), while Section C (p=0.636) and summed scores (p=0.54) did not change during the pandemic. The PA of the participants decreased (p=0.001), hours of sitting increased (p<0.001). While the body image, pain, and treatment satisfaction scores did not change; the function, mental health, subtotal, and total scores of the participants (respectively p=0.876, p=0.092, p=0.224, p=0.008, p<0.001, p<0.001, p<0.001) decreased. Conclusion: The rehabilitation adherence in individuals with IS was affected negatively, PA levels decreased, sedentary behaviors increased, and QoL of participants decreased during the pandemic. In addition to other factors, the decreased PA levels in the pandemic period may have negatively affected QoL and rehabilitation process in participants with IS. In the light of future studies, it may be recommended to give importance to physical activity as well as other factors in the rehabilitation of individuals with IS.