COVID-19 was declared a pandemic by the WHO in March 2020. The most promising strategy to control the pandemic was to develop a vaccine. However, vaccination hesitancy is a major threat to world public health. Understanding the reasons behind this hesitancy might help in developing encouragement strategies. This cross-sectional study aimed to assess the knowledge and attitude toward the COVID-19 vaccine in Saudi Arabia. A total of 1599 responses were received; the overall vaccine acceptancy was 79.2%. Age, sex, and nationality of participants significantly predicted the vaccination status. A significantly higher proportion of participants, who reported being vaccinated, or intended to receive the vaccine, stated that the COVID-19 infection is dangerous, or varies from person to person; the vaccine is safe, and think there is a definite need for the vaccine (p < 0.001). The major encouragement factors to receive the vaccine were either confidence in the government decisions (54.8%), or the feeling of responsibility to stop the pandemic (48.7%), whereas the main discouraging factors were concerns about the insufficient clinical trials (11.4%), or the undiscovered side effects (11%). The results of this study indicate good acceptance toward the COVID-19 vaccine among residents of Saudi Arabia.