Introduction: The effect of impaired nutritional status on the evolution of COVID-19 infection is not yet clear, but research already suggests that nutritional status can influence the individual risk of SARS-CoV-2 progression. In patients with COVID-19 and underlying cardiovascular disease, the respiratory symptoms of the infection are more severe and inflammatory levels may be markedly higher. The aim was to evaluate the effects of COVID-19 infection on the nutritional status of hospitalized cardiac patients. Methods: Cross sectional study on hospitalized cardiac patients with suspected or confirmed COVID-19 infection. The patients with confirmed COVID-19 constituted the case group, while the suspected patients with negative testing for COVID-19 constituted the comparison group. In both groups, we assessed the Body Mass Index (BMI), arm circumference (AC), calf circumference (CC), tricipital skinfold (TSF), arm muscle circumference (AMC), total lymphocyte count (TLC) and nutritional prognostic index (NPI). Results: A total of 32 patients were evaluated, with 18 cases. Malnutrition in patients with COVID-19 ranged from 30.8% (according to BMI) to 55.6% (according to AMC). At admission, mean BMI, AC, and TLC were lower in the case group (p<0.05). Comparing admission and discharge data, only the case group showed a significant reduction in AC and TSF (p<0.05). Nutritional variables did not correlate with length of stay in the two groups evaluated. Conclusion: Malnutrition was high in patients with COVID- 19, with marked muscle reserve impairment. Infected patients had lower mean BMI, AC, and TLC at hospital admission and had reduced anthropometric measurements (AC and TSF) at the end of hospitalization.