ABSTRACT: Objective: The COVID-19 pandemic is still continuing throughout the world, with newer genetic variants regularly appearing from different parts of the world. Considering the waning of immunity against COVID-19 infection even with two doses of the COVID-19 vaccine, regulatory authorities have authorised booster COVID-19 vaccination in many countries, especially for vulnerable populations, including healthcare workers. The current study analysed factors predicting the third (booster) dose of COVID-19 vaccine intention, including the health belief model (HBM), among the healthcare workers in Saudi Arabia. Methods: The current study was a cross-sectional online survey performed from 1st October 2021 to 30th November 2021, using a questionnaire prepared in GoogleTM form among healthcare workers in Saudi Arabia. The questionnaire asked demographic factors, COVID-19 experience of participants, subjective assessment of health, intention of COVID-19 booster dose vaccination, preferences for local/foreign-made vaccines, and health belief of the study population related to COVID-19 infection and COVID-19 booster dose. Results: This study received 2059 complete responses. The study population reported mixed health belief with respect to the susceptibility of COVID-19 infection, and higher health belief perception regarding the severity. The perceptions of the study participants regarding the benefits of COVID-19 booster dose were positive. There were few barriers to COVID-19 booster dose expressed by study participants. A total of 1464 (71.1%) study participants reported positive intent for receiving a COVID-19 booster dose. The study showed significant association between definite intention to receive a booster dose and nationality (p = 0.001), marital status (p = 0.017), gender (p < 0.001), education level (p = 0.001), monthly income (p < 0.001), and co-morbid medical illness (p = 0.045). The perception of the COVID-19 booster vaccine as a good idea to minimise worries about getting COVID-19 (OR = 2.28, CI 1.89-2.76), and perceptions that receiving the third (booster) dose reduces the risk of COVID-19 infection and associated complications (OR= 2.69, CI = 2.17-3.34), of the perceived benefit construct of HBM, predicted significantly higher definite intention to receive a booster dose. The concern with the safety of the vaccine (OR= 0.40, CI 0.34-0.47) under the perceived barriers construct of HBM predicted as significantly higher no definite intention to receive a booster dose. Conclusions: The results of the present study can guide policy makers in their efforts to promote booster doses of COVID-19 vaccination among the healthcare workers in Saudi Arabia.