Third sector organisations have been providing continuing professional development (CPD) for teachers in the UK in the field of global learning over decades. Given the patchy provision within initial teacher training, these organisations are the main source of support for teachers in helping their pupils engage with and respond to global issues. Drawing on qualitative and quantitative data from the Global Learning Programme in England (GLP-E 2013-18), this article investigates what teachers identify as valuable from the global learning CPD they received from organisations on the programme. Teachers value the specialist expertise, both in terms of global learning knowledge and pedagogy, the relationships they develop with global learning organisations, and the willingness of these organisations to collaborate for the benefit of schools. The findings demonstrate that there is potential for a greater contribution to teachers' global learning professional development within schools, but this requires more consistent, engagement with global learning organisations over the longer-term. To facilitate this, policymakers need to ensure a sustained funding environment both for schools and the global learning sector if teachers are to be sufficiently supported for working in an increasingly global and rapidly changing world.