BACKGROUND: We aimed to assess if discordance between patient-reported Kansas City Cardiomyopathy Questionnaire (KCCQ)-overall summary (os) score and physician-assessed New York Heart Association (NYHA) class is common among patients with heart failure (HF) with reduced or preserved ejection fraction, and determine its association with outcomes. METHODS: A total of 4818 patients with HF were classified according to KCCQ-os score (range 0-100, dichotomized by median value 71.9 into high [good] versus low [bad]) and NYHA class (I/II [good] or III/IV [bad]) as concordant good (low NYHA class, high KCCQ-os score), concordant bad (high NYHA class, low KCCQ-os score), discordant worse NYHA class (high NYHA class, high KCCQ-os score), and discordant worse KCCQ-os score (low NYHA class, low-KCCQ-os score). The composite of HF hospitalization or death at 1 year was compared across groups. RESULTS: There were 2070 (43.0%) concordant good, 1099 (22.8%) concordant bad, 331 (6.9%) discordant worse NYHA class, and 1318 (27.4%) discordant worse KCCQ-os score patients. Compared with concordant good, adverse outcomes were the highest in concordant bad (HR, 2.7 [95% CI, 2.2-3.5]) followed by discordant worse KCCQ-os score (HR, 1.8 [95% CI, 1.4-2.2]) and discordant worse NYHA class (HR, 1.5 [95% CI, 1.0-2.3]); with no modification by HF phenotype (preserved versus reduced ejection fraction, Pinteraction=0.52). At 6 months, 1403 (48%) experienced clinically significant improvement in KCCQ-os score (≥5 points increase over 6 months). Patients with improved KCCQ-os at 6 months (HR, 0.65 [95% CI, 0.47-0.92]) had better outcomes and the association was not modified by HF phenotype (Pinteraction=0.40). CONCLUSIONS: One-third of patients with HF had discordance between patient-reported and clinician-assessed health status, largely attributable to worse patient-reported outcomes. Such discordance, particularly in those with discordantly worse KCCQ, should alert physicians to an increased risk of HF hospitalization and death, and prompt further assessment for potential drivers of worse patient-reported outcomes relative to physicians' assessment.