Objectives: The study aimed to assess the national attitudes toward individuals with mental health illnesses in Saudi Arabia, exploring the relationship between these attitudes and various sociodemographic factors. Methods: A cross-sectional design with computer-assisted telephone interviews was employed, covering all 13 administrative regions in Saudi Arabia. A total of 4,533 adults agreed to participate, and their attitudes toward people with mental illnesses (PWMI) were measured using an 11-item scale. The translation of the original English version of the PWMI to Arabic was validated and published previously. The scale used level of agreement on a 5-point Likert scale. The score varies from 11 to 55, where a higher score signifies higher stigma. The associations between total PWMI scores and sociodemographic variables were analyzed using linear regression. Results: The mean age of participants was 35.92 ± 12.84, with equal distribution across regions. The linear regression model showed significant associations between total PWMI scores and gender, education level, marital status, living with, or being friends with someone diagnosed with a mental illness, and working in healthcare. No significant associations were found with age, income level, and previous mental health diagnosis. The study suggests that negative stereotypes about mental illness may be more prevalent in Saudi Arabia, while Saudi participants had a more optimistic view regarding the recovery and outcomes of mental illnesses. Conclusions: The study highlights the importance of assessing mental health stigma and its associations with sociodemographic factors in Saudi Arabia. The significant associations found point to the need for targeted interventions and public health campaigns to address misconceptions and stereotypes surrounding mental health, ultimately improving the societal acceptance and well-being of individuals with mental health illnesses.