Radical primary level curriculum reform is underway in Ireland. Many significant changes and additions include, for the first time, an explicit reference to global citizenship at primary level, an active citizen competency and several global learning themes. Research indicates that oftentimes, policy curriculum aspirations fail to materialise in the classroom due to insufficient attention to implementation and teacher ownership. Drawing on a mixed methods study comprising a national survey of Irish primary teachers (n = 288), this paper identifies important insights into teachers’ understandings of and capacity for GCE. The findings indicate highly positive teacher attitudes towards GCE, specifically its importance for pupils’ learning. The results also reveal that teachers’ understandings are multifaceted and nuanced, and informed by everyday experiences and contexts, as opposed to international or national frameworks. Significantly, we find a substantial proportion of teachers do not associate GCE with sustainability or behavioural dimensions and they rate their pedagogical skills low in the latter. The paper considers the implications of these findings within a policy context that inextricably connects GCE to action and sustainable development and in light of persistent challenges in extending the reach of GCE in schools.