Scoliosis, marked by abnormal spinal curvature, is common in adolescents and can lead to chronic pain and reduced quality of life. The relationship between physical activity and scoliosis is debated. In this study, we aim to investigate the causal relationship between physical activity levels and idiopathic scoliosis risk using the Mendelian randomization (MR) approach. Two-sample MR analyses evaluated low-intensity (low-intensity physical activity [LIPA]), moderate-to-vigorous (MVPA), and total physical activity (TLA) as exposures, selecting genetic instruments based on their associations. Total physical activity significantly associated with idiopathic scoliosis (OR = 1.72; 95% CI = 1.11–2.68; P = .015), whereas LIPA and MVPA showed no significant associations. Reverse MR found no idiopathic scoliosis impact on activity levels. Multivariable MR showed no significant activity-scoliosis links. Total physical activity emerges as an idiopathic scoliosis risk factor, warranting mechanistic exploration. LIPA and MVPA do not causally link to scoliosis. Idiopathic scoliosis does not influence activity levels.