Cardiovascular diseases can affect the clinical course of coronavirus disease 2019 (COVID-19); however, evaluation of COVID-19 contribution to prognosis for each individual disease, such as heart failure, is lacking in South Korea. Therefore, this study aimed to investigate COVID-19 patients with heart failure by matching them with patients with heart failure only and those with COVID-19 only. We performed a nationwide population-based retrospective study using data from the National Health Insurance System. Based on patients with heart failure and COVID-19, up to 1:3 propensity score matching procedures were performed for patients with heart failure only and those with COVID-19 only. The outcome was the composite of complications. After matching, a multivariable-adjusted conditional logistic regression analysis was performed. The number of patients was 317 for heart failure and COVID-19, 951 for heart failure only, and 884 for COVID-19 only. The adjusted odds ratio (OR) and 95% confidence interval (CI) for the composite of complications of patients with heart failure and COVID-19 compared with those with heart failure only was 3.511 (2.501-4.928), and compared with those with COVID-19 only, they were 1.626 (1.112-2.376). In patients with heart failure and COVID-19, age per 10 years increase and diabetes were significant variables with the adjusted OR (95% CI) [2.206 (1.704-2.856) for age and 2.345 (1.244-4.420) for diabetes] for complications. This study demonstrated that patients with both heart failure and COVID-19 in South Korea are associated with a poor prognosis. Patients with heart failure require more surveillance and precautions for COVID-19, as recommended by the Center for Disease Control and Prevention.