There have been repeated calls to include mental health in the sustainable development goals (SDGs), arguing that progress in development will not be made without improvements in mental health. Although these calls are starting to gain political traction, currently only a tiny fraction of international development work includes mental health. A social determinants framework may be useful in incorporating mental health into sustainable development because it promotes a multi-sectorial and multi-disciplinary approach which is the corner stone of good development practice. Two approaches are suggested to make mental health a part of sustainable development: (1) integrate mental health into existing development programmes to promote social and economic environments that prevent mental health problems developing; (2) ensure that mental health programmes are better at promoting sustainable development by preventing the negative social and economic consequences of mental illness. Real-world examples of these approaches are provided. To achieve this, the mental health impact of wider development programmes, and the social and economic consequences of mental health interventions, must be evaluated. Development agencies should ensure that they have equity for mental health in all their policies, and investment must be increased for those mental health prevention, promotion and treatment programmes which have the greatest impact on sustainable development. The SDGs bring the promise of a more holistic approach to development. It is now the task of global mental health to demonstrate not just that mental health is an integral part of sustainable development, but that affordable and effective solutions exist which can improve mental health and development more broadly.