<b><i>Introduction:</i></b> Given that mental health services are developing across Gulf Cooperation Council (GCC) or Arab Gulf countries, there is a need to examine the nature of these services to explore how they are developing, expanding, or evolving. This study aimed to explore what is known about the scope and nature of available mental health services for adult populations in Arab Gulf countries. <b><i>Methods:</i></b> This scoping review was informed by the 2005 methodological framework of Arksey and O’Malley. The databases MEDLINE, PsycINFO, CINAHL, ProQuest Central, EMBASE, Web of Science/Scopus, DOAJ, and Saudi Digital Library were searched for studies published between 2011 and 2021. Studies were included if they focused on reported scope and nature of available mental health services for adult populations in Arab Gulf countries, excluding those related to drug and alcohol, intellectual disability, and behavioural problems. <b><i>Results:</i></b> The search identified 8,884 articles, from which a total of 28 were included in the final review. The majority of studies were from the Kingdom of Saudi Arabia, with fewer studies from other Arab Gulf countries, and only one conducted in Bahrain. Mental health services described were primarily referral services, psychotherapy and cognitive behavioural therapy, telepsychiatry and mobile health services, screening, early detection and management of depression and anxiety, and other mental health services. <b><i>Conclusion:</i></b> This review revealed that the most available and utilised mental health services in Arab Gulf countries for treating adult mental disorders are psychotherapy and cognitive behavioural therapy, telepsychiatry and mobile health services, especially during the COVID-19 pandemic.