Background: Structural changes caused by spinal curvature may impact the organs within the thoracic cage, including the heart. Cardiac abnormalities in idiopathic scoliosis patients are often studied post-corrective surgery or secondary to diseases. To investigate cardiac structure, function, and outcomes in participants with scoliosis, phenotype and imaging data of the UK Biobank (UKB) adult population cohort was analysed. Methods: Hospital episode statistics of 502,324 adults were analysed to identify participants with scoliosis. Summary 2D cardiac phenotypes from 39,559 cardiac magnetic resonance imaging (CMR) scans were analysed alongside a 3D surface-to-surface (S2S) analysis. Results: A total of 4,095 (0.8%, 1 in 120) UKB participants were identified to have all-cause scoliosis. These participants had increased lifetime risk of major adverse cardiac events (MACE) (HR=1.45, P<0.001), driven by heart failure (HR=1.58, P<0.001) and atrial fibrillation (HR=1.54, P<0.001). Increased radial and decreased longitudinal peak diastolic strain rates were identified in participants with scoliosis (+0.29, Padj<0.05; -0.25, Padj<0.05; respectively). Cardiac compression of the top and bottom of the heart and decompression of the sides was observed through S2S analysis. Additionally, associations between scoliosis and older age, female sex, heart failure, valve disease, hypercholesterolemia, hypertension, and decreased enrolment for CMR, were identified. Conclusion: The spinal curvature observed in participants with scoliosis alters the movement of the heart. The association with increased MACE may have clinical implications for whether to undertake surgical correction. This work identifies, in an adult population, evidence for altered cardiac function and increased lifetime risk of MACE in participants with scoliosis. Future genetic analyses would aid to assess causality.