Background The impact on survival of gadoxetic acid-enhanced MRI in addition to multiphase contrast material-enhanced CT for initial staging in patients with hepatocellular carcinoma (HCC) is unknown. Purpose To compare all-cause mortality in patients with HCC who underwent CT only, CT plus non-gadoxetic acid-enhanced MRI, or CT plus gadoxetic acid-enhanced MRI as part of their initial diagnostic work-up. Materials and Methods The authors performed a nationwide retrospective cohort study of patients diagnosed with HCC in South Korea between January 2008 and December 2010. Follow-up extended through December 2014. The primary outcome was all-cause mortality. Cox proportional hazards regression model with adjustment of confounding factors was used to estimate hazard ratios (HRs) for all-cause mortality. Results Among 30 023 patients with HCC (mean age ± standard deviation, 58.5 years ± 10.7, 23 978 men), the proportions of patients in whom HCC was diagnosed using CT only, CT plus non-gadoxetic acid-enhanced MRI, and CT plus gadoxetic acid-enhanced MRI were 56.1%, 12.9%, and 31.0%, respectively. In adjusted analysis using CT only as the reference category, the HR for mortality for CT plus gadoxetic acid-enhanced MRI was 0.64 (95% confidence interval [CI]: 0.62, 0.67; P < .001), and the HR for CT plus non-gadoxetic acid-enhanced MRI was 0.71 (95% CI: 0.68, 0.75; P < .001). Use of CT plus gadoxetic acid-enhanced MRI was associated with lower mortality compared with CT plus non-gadoxetic acid-enhanced MRI (adjusted HR, 0.90; 95% CI: 0.85, 0.95; P < .001), but this survival advantage was restricted to patients with localized disease. Conclusion In patients with hepatocellular carcinoma, additional use of contrast-enhanced MRI was associated with lower mortality. Furthermore, CT plus gadoxetic acid-enhanced MRI was associated with better survival than CT plus non-gadoxetic acid-enhanced MRI but only in patients with localized disease. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Kim in this issue.