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Background Cardiac magnetic resonance (CMR) tissue characterisation is increasingly used to improve prognostic risk stratification in heart failure with preserved ejection fraction (HFpEF). While both T1 mapping and extracellular volume (ECV) reflect diffuse myocardial fibrosis, their relative prognostic evidence has not been systematically compared.Methods In a PROSPERO-registered systematic review, we searched MEDLINE, EMBASE, Web of Science, and Cochrane CENTRAL for relevant studies. Studies enrolling adults with HFpEF (LVEF ≥50%) reporting CMR-derived T1 mapping and clinical outcomes were included. Prognostic effect estimates, hazard ratios (HRs) were extracted where available. ECV focusing studies were analysed in parallel to benchmark evidentiary maturity and quantitative robustness.Results Seven HFpEF cohorts evaluating T1 mapping were identified, comprising 900 patients (mean age 66–79 years, 55–65% female), with median follow-up ranging from 18 to 36 months. Across studies, higher native or post-contrast T1 values were consistently observed in patients experiencing adverse outcomes, with reported differences of 40–100 ms between event and no-event groups (all p values <0.05). However, only 2/7 studies (29%) reported extractable time-to-event analyses, yielding heterogeneous and imprecise hazard ratios (HR range 1.0–2.4) that precluded pooled meta-analysis.In contrast, five ECV studies including approximately 770 HFpEF patients (mean age 68–78 years, 60% female) consistently reported multivariable-adjusted HRs for mortality and/or heart-failure hospitalisation. Quantitative synthesis demonstrated robust prognostic associations, with pooled HRs ranging from 1.2 to 1.7 and evidence of dose–response relationships.Conclusion Although T1 mapping demonstrates a consistent biological signal in higher-risk HFpEF patients, its prognostic translation is limited by sparse and inconsistent survival modelling. Compared with ECV, T1 mapping remains underdeveloped for clinical risk stratification. Standardised T1-based prognostic reporting is required to enable integration of CMR tissue characterisation into HFpEF imaging pathways and trials.