The lack of treatment options for COVID-19 has raised many concerns among populations worldwide, which has led to many attempts to find alternative options to prevent the transmission of the disease or to alleviate the progression of the infection, including focusing more on preventive measures (to prevent transmission to other individuals) and the use of natural products and herbal extracts to increase immunity and decrease the probability of getting infected. This study explored the knowledge of the population of the Kingdom of Saudi Arabia (KSA) about COVID-19 preventive measures and their belief about the consumption of herbal products for the prevention of COVID-19 infection. A total of 5,258 individuals participated in this study. Participants' knowledge about the appropriate COVID-19 preventive measures in terms of handwashing procedures, self-quarantine and social distancing was moderate, with a mean score of 5.5 (SD: 1.7) out of 10 (representing around 55.0% of the total score). About 22.1% (n = 1,161) of the participants reported that they have used herbal products or nutritional supplements during the pandemic period, to protect themselves from the disease. Social media and the Internet (39.4%, n = 372) were the main motivators for the participants to try herbal products. Vitamin C was the most commonly used food supplement to increase immunity and reduces the chance of contracting COVID-19. Our study demonstrated that the general population in Saudi Arabia has a moderate level of knowledge about COVID-19 transmission and preventive measures. A considerable proportion of the population reported the use of herbal products or food supplements in order to protect themselves from the disease. Policymakers are suggested to provide further educational campaigns that increase population knowledge about the disease transmission routes and preventive measures. In addition, the use of herbal products should be evidence-based to ensure patient safety.