Description: Aims Heart failure (HF) quality registries report quality of care but it is unknown whether they improve outcomes. The aims were to assess predictors of enrolment in a HF registry, test the hypothesis that enrolment in a HF registry is associated with reduced mortality, and assess potential explanatory factors for this reduction in mortality, if present. Methods and results We conducted a nationwide prospective cohort study of patients with new-onset HF registered in the Swedish National Patient Registry (NPR, a mandatory registry of ICD-code diagnoses) with or without concurrent registration in the Swedish Heart Failure Registry (SwedeHF, a voluntary quality reporting registry) 2006–2013. The association between demographics, co-morbidities and medications, and enrolment in the SwedeHF, was assessed using multivariable logistic regression. The association between enrolment in the SwedeHF and all-cause mortality was assessed using multivariable Cox regression, with adjustment for demographics, co-morbidities and medications. A total of 231 437 patients were included, of which 21 888 (9.5%) were in the SwedeHF [age (mean ± standard deviation) 74 ± 13 years; 41% women; 68% inpatients] and 209 549 (90.5%) were not (age 78 ± 12 years, 50% women; 79% inpatients). Selected variables independently associated with enrolment in the SwedeHF were male sex, younger age, higher education, absent co-morbidities and co-morbidity-related medications, and use of HF and cardiovascular medications. Over a median (interquartile range) follow-up of 874 (247–1667) days, there were 13.0 vs. 20.8 deaths per 100 patient-years ( P  〈 0.001). The hazard ratio (95% confidence interval) for death for the SwedeHF yes vs. no was 0.65 (0.63–0.66) crude, and increased to 0.80 (0.78–0.81) after adding demographics, to 0.82 (0.80–0.84) after adding co-morbidities and co-morbidity-related medications, to 0.95 (0.93–0.97) after adding cardiovascular medications, and to 1.04 (1.02–1.07) after adding HF-specific medications. Conclusion Heart failure patients of male sex, younger age, and higher education were more likely to be enrolled in a HF quality registry. Enrolment was associated with reduced all-cause mortality that was explained by demographic differences and better utilization of cardiovascular and HF medications.