The impact of the novel coronavirus disease 2019 (COVID-19) pandemic on diet and nutrition among older adults with chronic medical conditions have not been well-described. We conducted a survey addressing (1) food access, (2) diet quality and composition, (3) nutritional understanding, and (4) attitudes towards research among adults with heart failure (HF) within an integrated health system. Adults (≥18 years) with diagnosed HF and at least one prior hospitalization for HF within the last 12 months were approached to complete the survey electronically or by mail. Outcomes included all-cause and HF-specific hospitalizations and all-cause death was ascertained via the electronic health record. Among 1212 survey respondents (32.5% of eligible patients) between May 18, 2020 and September 30, 2020, mean ± SD age was 77.9 ± 11.4 years, 50.1% were women, and median (25th-75th) left ventricular ejection fraction was 55% (40%-60%). Overall, 15.1% of respondents were food insecure, and only 65% of participants answered correctly more than half of the items assessing nutritional knowledge. Although most respondents were willing to participate in future research, that number largely declined for studies requiring blood draws (32.2%), study medication (14.4%), and/or behavior change (27.1%). Food security, diet quality, and nutritional knowledge were not independently associated with outcomes at 90 or 180 days. In a cohort of older adults with HF and multiple comorbidities, a significant proportion reported issues with food access, diet quality, and nutritional knowledge during the COVID-19 pandemic. Future research should evaluate interventions targeting these domains in at-risk individuals.