The importance and need for education for sustainability (EfS) are recognised in the New Zealand Curriculum. Teachers face challenges, however, due to lack of support and professional learning about how to integrate EfS in school curricula. Social media can be used for teacher professional learning (TPL), and communication and resources can be combined to create flexible collaborative learning opportunities. However, there is little evidence to date of social media being used for TPL in EfS. Based on findings from a wider study exploring teachers' perceptions of professional learning through social media in EfS, this paper focuses on how social media facilitates flexible TPL in EfS. The study adopted a mixed-methods approach using questionnaires, interviews, and a combination of document analysis and interviews in three phases. Findings from Phases 1 and 2 suggest that participants see TPL through social media as offering flexibility, and being useful for collaborative learning and support for teachers. In Phase 3, these findings are used to design and establish TPL for EfS teachers using Google+ to facilitate synchronous and asynchronous interactions between teachers, EfS experts, and resources. Although participants understood the flexibility of social media for enabling collaboration and providing support opportunities in EfS, the use of social media for professional learning is particularly attractive for teachers who work in rural and remote areas.