Background: There are limited data on the attitudes and acceptance of the second booster (fourth dose) of the COVID-19 vaccination among physicians. Methods: A cross-sectional, questionnaire-based, online study was conducted among members of the Athens Medical Association (A.M.A.) who were invited to participate anonymously over the period from January to March 2023. Results: From the 1224 members who participated in the survey, 53.9% did not receive the fourth dose of the COVID-19 vaccine. The main reasons for no vaccination were the lack of obligation to receive the fourth dose, the history of three doses of the COVID-19 vaccine and the lack of sufficient information about the effectiveness of the fourth dose. Over half of the three-dose-vaccinated participants were willing to receive the fourth dose in the near future. Interestingly, the vaccination coverage among participants who had been informed about the fourth dose through scientific sources was low. Conclusions: The low vaccination coverage with the fourth dose reported in this study can lead to broad and serious consequences, such as increase in COVID-19 infections, reduction of available healthcare staff and increased caseloads of COVID-19 in hospitals. Furthermore, hesitant physicians will adversely influence the vaccination uptake among the general population due to their key role in informing and recommending the vaccine. The healthcare system administration should acknowledge and address physician’s concerns through effective communication and better support.