Objectives: This study sought to investigate the relationship between malnutrition and adverse cardiovascular (CV) events in heart failure with preserved ejection fraction (HFpEF). Background: Malnutrition is associated with poor prognosis in a wide range of illnesses, however, the prognostic impact of malnutrition in HFpEF patients is not well known. Methods: Baseline malnutrition risk was determined in 1,677 patients with HFpEF enrolled in the Americas regions of the TOPCAT (Aldosterone Antagonist Therapy for Adults With Heart Failure and Preserved Systolic Function) trial, according to 3 categories of the geriatric nutritional risk index (GNRI) as previously validated: moderate to severe, GNRI of <92; low, GNRI of 92 to <98; and absence of risk, GNRI of ≥98. The relationships between malnutrition risk and the primary composite outcome of CV events (CV death, heart failure hospitalization, or resuscitated sudden death) and all-cause death were examined. Results: Approximately one-third of patients were at risk for malnutrition (moderate to severe: 11%; low: 25%; and absence of risk: 64%). Over a median of 2.9-years’ follow-up, compared to those with absent risk for malnutrition, moderate to severe risk was associated with significantly increased risk for the primary outcome, CV death and all-cause death (hazard ratio [HR]: 1.34; 95% confidence interval [CI]: 1.02 to 1.76; HR: 2.06; 95% CI: 1.40 to 3.03; and HR: 1.79; 95% CI: 1.33 to 2.42, respectively) after multivariate adjustment for age, sex, history of CV diseases, and laboratory biomarkers. Conclusions: Patients with HFpEF are at an elevated risk for malnutrition, which was associated with an increased risk for CV events in this population.