Background Both ST-segment resolution (STR) and myocardial blush grade (MBG) have prognostic utility after primary percutaneous coronary intervention (PCI) for ST-elevation myocardial infarction. We sought to clarify how frequently MBG and STR provide discordant measures of reperfusion success and to determine the independent prognostic significance of each on long-term outcomes. Methods In HORIZONS-AMI, core laboratory measures of both MBG and STR were assessed in 2,367 patients undergoing primary PCI. Four groups were identified based on MBG (grades 2/3 vs 0/1) and STR (≥50% vs <50%). A multivariable model identified predictors of death and major adverse cardiac events at 3 years. Results Myocardial blush grade 2/3 was achieved in 77.7% of patients, and STR ≥50% was achieved in 75.1% of patients. Myocardial blush grade and STR were discordant in 765 patients (30.9%). By multivariable analysis, MBG 2/3 compared with 0/1 was an independent predictor of lower mortality at 3 years (4.4% vs 8.4%, adjusted hazard ratio HR = 0.57 0.39, 0.82, P = .003). In contrast, STR ≥50% compared with <50% was not associated with mortality (5.1% vs 5.9%, adjusted HR = 1.11 0.68, 1.56, P = .89). However, repeated revascularization at 3 years was less frequent when STR ≥50% (12.4% vs 17.6%, adjusted HR = 0.74 0.58, 0.95, P = .02). In contrast, MBG 2/3 vs 0/1 was not associated with reduced repeated revascularization (13.6% vs 14.1%, adjusted HR = 1.02 0.79, 1.33, P = .85). Conclusions In HORIZONS-AMI, MBG and STR after primary PCI were concordant in only 70% of patients and provided complementary prognostic information. Myocardial blush grade predicted long-term survival, whereas STR predicted freedom from repeated revascularization.