Background: New SARS-CoV-2 variants have emerged and COVID-19 is still a public health issue, especially for vulnerable groups such as people with chronic medical conditions. Objective: To investigate the impact of COVID-19-related burnout on COVID-19 vaccination intention in cardiac patients. Moreover, we investigated other possible demographic and psychological predictors of vaccination intention in cardiac patients. Methods: We conducted a cross-sectional study in Greece using a convenience sample. Data collection was performed from 20 November 2022 to 10 January 2023. We measured demographic data, COVID-19-related burnout, anxiety, depression, social support, and resilience. We used the following valid tools: COVID-19 burnout scale, Patient Health Questionnaire-4, Multidimensional Scale of Perceived Social Support, and Brief Resilience Scale. Results: Among patients, 45.8% were willing to accept a COVID-19 booster dose, 25.3% were hesitant, and 28.9% were unwilling. Patients experienced moderate levels of COVID-19-related burnout. After multivariable linear regression analysis, we found that increased age and decreased emotional exhaustion due to COVID-19 were associated with increased vaccination intention. Moreover, patients who have already received a booster dose had also a greater willingness to accept a new booster dose. Conclusions: Identification of factors that influence patients decision to accept a COVID-19 booster dose is crucial to maintain a high vaccination coverage rate among them in order to avoid COVID-19-related outcomes. Since a COVID-19 booster dose on an annual basis seems to be necessary policy makers should develop and implement vaccination programmes tailored for patients.