Mental disorders represent the leading cause of disability worldwide, yet they remain a low global health priority. This paper uses a case study methodology and different data sources (35 interviews and documents) to analyse factors that have shaped the generation of political priority for global mental health over the past three decades (1990–2020) and their changes over time. The Shiffman and Smith framework on determinants of political priority for global health issues is used to organise data into themes: actor power, ideas, political context, and issue characteristics. Global mental health has gained political attention especially over the past decade, yet support remains limited. Findings reveal that actor power is undermined by a fragmented policy community, absence of one guiding institution or coordination mechanism, and little civil society mobilisation. Public portrayal of the issue is divided, hampered by the absence of a common understanding by the community, and by stigma. Some policy windows have been missed and a strong global governance structure is lacking. Credible indicators and evidence on simple cost-effective solutions especially in low- and middle-income countries are scarce. However, opportunities are arising, including an increasing number of leaders and grassroot organisations, multiple arguments for action and integrated solutions resonating with broader audiences, widening political support at national level, an emerging global governance structure, and an expanding evidence base on the scale of the problem and available solutions. The results points to three technical and four political challenges that advocates need to address to increase political support over the next decade.