Background Ischemic late gadolinium enhancement (LGE) assessed with cardiac MRI is a well-established prognosticator in ischemic cardiomyopathy. However, the prognostic value of additional LGE parameters, such as extent, transmurality, location, and associated midwall LGE, remains unclear. Purpose To assess the prognostic value of ischemic LGE features to predict all-cause mortality in ischemic cardiomyopathy. Materials and Methods This study is a secondary analysis of a prospective dual-center trial of participants with ischemic cardiomyopathy and left ventricular ejection fraction (LVEF) under 50% referred for viability assessment using cardiac MRI between 2008 and 2022. The LGE granularity parameters (extent of ischemic LGE, transmurality, location, and associated midwall LGE) assessed by cardiac MRI experts were compared with traditional prognosticators of adverse events in ischemic cardiomyopathy (age, sex, body mass index, diabetes, smoking, dyslipidemia, heart failure hospitalization, atrial fibrillation, renal failure, known myocardial infarction, and LVEF). The primary outcome was all-cause mortality. Predictive value was evaluated using Cox regression analysis and assessed using time-dependent receiver operating characteristic curves at 10 years. The cardiac MRI LGE score was developed using LGE granularity parameters. Results Among 6082 participants (mean age, 64.5 years ± 11.8 [SD]; 4419 men), 3591 had ischemic LGE. During a median follow-up of 9.0 years (IQR, 6.6-11.5 years), 652 participants died. The presence of ischemic LGE was strongly associated with mortality (hazard ratio, 3.45 [99.5% CI: 2.55, 4.67]; P < .001). In the group with ischemic LGE, the LGE granularity model combining these LGE features showed the best predictive value above traditional prognosticators and ischemic LGE extent to predict all-cause mortality (area under the receiving operating characteristic curve [AUC] at 10 years, 0.89 [99.5% CI: 0.89, 0.90] vs 0.83 [99.5% CI: 0.83, 0.84]; P < .001). The cardiac MRI LGE score performed well in participants with ischemic LGE (AUC at 10 years, 0.87 [99.5% CI: 0.85, 0.90]). Conclusion In a large cohort of participants with ischemic cardiomyopathy, an LGE granularity model had a higher prognostic value over traditional prognosticators to predict mortality. © RSNA, 2025 Supplemental material is available for this article. See also the editorial by Lima and Ebrahimihoor in this issue.