Against the backdrop of mounting calls for the global scaling-up of mental health services – including quality care and prevention services – there is very little guidance internationally on strategies for scaling-up such services. Drawing on lessons from scale-up attempts in six low- and middle-income countries, and using exemplars from the front-lines in South Africa, we illustrate how health reforms towards people-centred chronic disease management provide enabling policy window opportunities for embedding mental health scale-up strategies into these reforms. Rather than going down the oft-trodden road of vertical funding for scale-up of mental health services, we suggest using the policy window that stresses global policy shifts towards strengthening of comprehensive integrated primary health care systems that are responsive to multimorbid chronic conditions. This is indeed a substantial opportunity to firmly locate mental health within these horizontal health systems strengthening funding agendas. Although this approach will promote systems more enabling of scaling-up of mental health services, implications for donor funders and researchers alike is the need for increased time commitments, resources and investment in local control.