Heart failure is the main cause of hospitalization, which burdens the healthcare system. Although many hospitalizations for heart failure follow ambulance use, it is unknown whether ambulance use increases hospitalization costs. Using the Diagnosis Procedure Combination database in Japan, we examined all hospitalizations of patients with heart failure from April 2014 to March 2015. Patients were divided into those with and those without ambulance use. We performed a multiple regression analysis to examine the association between ambulance use and total hospitalization costs, adjusting for age, sex, length of day, and activities of daily living. We identified 126,067 hospitalizations for heart failure. The percentages of ambulance use were 29%, 27%, 30%, and 50% among patients with NYHA Functional Classification I, II, III, and IV, respectively. For patients categorized as NYHA I (n = 9,700), multiple linear regression analysis revealed that ambulance use was significantly associated with higher hospitalization cost (coefficient 723 USD; 95% confidence interval 109–1337; p = 0.021). Even for heart failure patients with NYHA I, ambulances were frequently used. Ambulance use was independently associated with increased hospital costs. Future research is needed on transitional care to limit unnecessary ambulance use.