BACKGROUND: Atrial fibrillation (AF) frequently complicates heart failure (HF), and each is associated with lower overall health-related quality of life. We aimed to quantify the incremental burden of AF on the health-related quality of life of patients with HF in clinical practice. METHODS AND RESULTS: We used data from the Utah mEVAL program to analyze patient-reported outcomes (PROs) among patients with HF with and without AF. The primary outcome was the HF-specific Kansas City Cardiomyopathy Questionnaire, with generic PROs as secondary outcomes. Among 1707 patients with HF, 36% had AF (n = 616). Those with HF and AF were older (mean age 69 years vs 58 years, P < .001), more likely to have prior stroke (29% vs 17%, P < .001) and ischemic cardiomyopathy (28% vs 23%, P = .01), but had similar ejection fractions (mean 44% each, P = .6). After adjustment, and compared with HF alone, HF with AF was associated with worse Kansas City Cardiomyopathy Questionnaire scores (adjusted mean difference -3.45, 95% confidence interval [CI] -6.24 to -0.65), and worse Patient-Reported Outcomes Measurement Information System physical function scores (adjusted mean difference -1.63, 95% CI -2.59 to -0.67). The difference in visual analog scale general health was borderline (adjusted mean difference -2.01, 95% CI -4.51 to 0.49), and Patient-Reported Outcomes Measurement Information System depression scores were similar (adjusted mean difference 0.54, 95% CI -0.48 to 1.57). CONCLUSIONS: AF complicates nearly one-third of HF cases, and patients with HF and AF are substantially older and sicker. After adjustment, AF was independently associated with worse disease-specific and overall health-related quality of life than HF alone. Whether maintaining sinus rhythm can improve the HF-related health status of patients with HF in clinical practice should be explored further.