In patients with hypertrophic cardiomyopathy, the prognostic value of myocardial T1 and extracellular volume fraction for adverse cardiovascular events has not been well defined.A total of 663 consecutive participants with hypertrophic cardiomyopathy who underwent 3T cardiovascular magnetic resonance were recruited. The follow-up end points included heart failure (HF)-related death, HF hospitalization, and sudden cardiac death or aborted sudden cardiac death.On Cox proportional hazards regression multivariable analyses, global native T1 excluding late gadolinium enhancement areas (hazard ratio [HR], 1.04 [95% CI, 0.99-1.09]; P=0.094) and global extracellular volume fraction excluding late gadolinium enhancement (HR, 1.02 [95% CI, 0.95-1.10]; P=0.565) were not associated with sudden cardiac death. Conversely, global native T1 (HR, 1.08 per 10 ms increase [95% CI, 1.02-1.16], P=0.014; HR, 1.05 per 10 ms increase [95% CI, 1.01-1.09]; P=0.009) and global extracellular volume fraction (HR, 1.23 per 1% increase [95% CI, 1.11-1.36], P<0.001; HR, 1.10 per 1% increase [95% CI, 1.04-1.16]; P<0.001) were independently associated with HF-related death and the composite end point of HF-related death or HF hospitalization in multivariable Cox models, respectively.In this study of patients with hypertrophic cardiomyopathy, we found global native T1 and global extracellular volume fraction (excluding late gadolinium enhancement) to be both independently associated with HF-related events, but not sudden cardiac death in multivariable analysis. These findings are hypothesis-generating and will require external validation in larger cohorts.URL: https://www.chictr.org.cn; Unique identifier: ChiCTR1900024094.