Background: Several observational studies have found that moderate chocolate consumption is associated with a lower risk of incidence of stroke and myocardial infarction and beneficial effects on lipid metabolism and endothelial function. Randomized clinical trials have shown that chocolate reduces systolic and diastolic blood pressure. One study showed that moderate chocolate consumption is associated with a lower rate of heart failure (HF) in women, but there have been no studies to evaluate the association between chocolate intake and incidence of HF in men. Methods and Results: We conducted a prospective cohort study of 33,028 men 45-79 years old with no history of myocardial infarction, diabetes, or HF at baseline who were participants in the population-based Cohort of Swedish Men (COSM) study. Chocolate consumption was assessed through a self-administrated food frequency questionnaire. Participants were followed for HF hospitalization or mortality from January 1, 1998 to December 31, 2011 using record linkage to the Swedish inpatient and cause-of-death registries. During 14 years of follow up, 1350 men were hospitalized (n = 1256) or died from incident HF (n = 192). We used Cox proportional hazards models to compute multivariable-adjusted rate ratios accounting for age, total caloric intake, education, BMI, physical activity, cigarette smoking, alcohol consumption, family history of myocardial infarction, self-reported history of hypertension, and self-reported history of high cholesterol. Compared with subjects who reported no chocolate intake, the multivariable-adjusted rate ratio of HF was 0.90 (95% CI 0.75 - 1.08) for those consuming 1-3 servings per month, 0.88 (95% CI 0.72 - 1.08) for those consuming 1-2 servings per week, 0.69 (95% CI 0.51 - 0.93) for those consuming 3-6 servings per week, and 1.14 (95% CI 0.77 - 1.69) for those consuming and ≥1 servings per day (P for quadratic trend=0.02). Conclusions: In this large prospective cohort study, there was a J-shaped relationship between chocolate consumption and HF incidence. Moderate chocolate consumption was associated with a lower rate of HF hospitalization or death, but the protective association was not observed among individuals consuming one or more servings per day.