Background <p>Mental and substance use disorders represent a significant public health challenge worldwide. In Saudi Arabia also a high burden of disease associated with mental disorders accounted for about 7.3% of the total burden of disease in the country. This study aimed to assess the temporal trends of prevalence, incidence, years-lived with disability (YLDs), and disability-adjusted life-years (DALYs) rates due to mental and substance use disorders over a 30-year period in Saudi Arabia.</p> Method <p>The data was obtained from The Global Burden of Disease (GBD) 2019. The GBD provided inclusive and accessible epidemiological data on 369 diseases and injuries, as well as 87 risk factors, from 1990 to 2019.</p> Results <p>In 2019, there were 5,032,669 (95%) uncertainty intervals (UI) 3·5–9·9)) adults in Saudi Arabia with mental disorder, and 166,989 with substance use disorder. The largest proportion of prevalence increase from 1990 to 2019 was in eating disorder with 9.8% (95% UI 7.03–12.6). The most significant proportion of prevalence and incidence increase from 1990 to 2019 was in opioid disorders with 41.08% change in prevalence and 36.83 in incidence. From 1990 to 2019 there was + 26.46% increase in the annual change rate of age standardized DALYs due to substance use disorders.</p> Conclusion <p>Mental disorders have a significant negative impact on large proportion of Saudis. While substance use disorder had moderate prevalence, it has been increasing rapidly since 2016. It is crucial for health officials and policymakers to make substantial investments in mental health and substance use services to promote prevention when possible and to offer accessible treatment, care, and rehabilitation. Efforts should also focus on integrating mental and physical health services.</p>