Background: Limited data exist regarding left ventricular remodeling patterns observed in adult survivors of childhood cancer after therapy. Methods: Among 1190 adult survivors diagnosed with childhood cancer (median age at diagnosis, 9 years [interquartile range (IQR), 3.8-14.4 years]; age at evaluation, 35.6 years [IQR, 29.5-42.8 years]), treatment exposures included anthracyclines (n = 346), chest radiotherapy (n = 174), both (n = 245), or neither (n = 425). Prospective echocardiographic assessment compared survivors with 449 noncancer controls classified according to left ventricle geometric patterns. Associations between left ventricle geometric patterns and decreased exercise tolerance were assessed. Results: Overall, 28.2% of survivors (95% confidence interval [CI], 25.6%-30.8%) exhibited concentric remodeling, 2.4% (95% CI, 1.6%-3.5%) exhibited eccentric hypertrophy, and 1.1% (95% CI, 0.6%-1.9%) exhibited concentric hypertrophy. A greater proportion of survivors who received only chest radiotherapy (41%) had concentric remodeling compared with those who received only anthracyclines (24%), both (27%), or neither (27%; all P <.001), and all were greater than the proportions in noncancer controls (18%; all P <.05). Concentric remodeling was associated with radiation exposure, but not with anthracycline exposure, in multivariable models. Survivors who had concentric remodeling were more likely to have a maximal oxygen uptake peak <85% compared with those who had normal geometry (81.0% vs 66.3%; odds ratio, 1.75; 95% CI, 1.15-2.68). Conclusions: Chest radiation therapy, but not anthracycline therapy, increased the risk for concentric remodeling in survivors of childhood cancer. The presence of concentric remodeling was associated with increased exercise intolerance.