Background: COVID-19 vaccination is a crucial public health intervention to stem the pandemic, however, there is a public hesitation to take the vaccine all over the world because of concerns about safety. Objective(s): To assess the intention to take COVID-19 vaccines among adults in Saudi Arabia, and to explore determinants of this intention and causes of refusal of COVID-19 vaccines. Methods: A cross-sectional study was conducted among 1345 adults in all provinces of Saudi Arabia using a questionnaire that was distributed via all social media channels. Stepwise binary logistic regression analysis was performed to identify the predictors to accept COVID-19 vaccination. Results: About 48% of respondents intend to receive COVID-19 vaccines. The predictors of COVID-19 vaccines acceptance were perception of strong possibility of getting COVID-19 infection, high risk perception of the COVID-19, adherence to protective measures during the pandemic, receiving flu vaccines and high level of knowledge. The three most common causes of refusal to receive COVID-19 vaccines were fear from side effects of vaccines (76.8%), absence of trust that it will prevent COVID-19 infection (44%) and being in good health (28.7%). Conclusion and recommendations: The willingness of adults to receive COVID-19 vaccines is suboptimal. There is a need for targeted health education messages using a multidisciplinary team capable of good communication with the public and dissemination of accurate messages via all social media platforms to correct misconceptions about the vaccines especially that related to public confidence in vaccine safety.