Young children's engagement in Education for Sustainability has focussed predominantly on their participation in environment-based initiatives or practices. Reasons for this include a notion that wider dimensions of sustainability, including social, political and economic areas of concern can be too complex and overwhelming for young children. When children experience learning around wider dimensions of sustainability, there is potential to develop genuine and critical understandings about global issues in a transformative and critical learning context. This article investigates how an early childhood teacher, in the role of teacher-as-researcher, engaged young children in a kindergarten classroom in an investigation of poverty as a socio-political aspect of sustainability. The authors focus on teacher-as-researcher critical reflections from action research data to contextualise how curriculum decision-making unfolded. Using critical theory as a guiding framework, the authors examine how knowledge around poverty was co-constructed between children and adults, thus unsettling the idea of teacher as 'expert'. The authors advocate for early childhood teachers to employ a teacher-as-researcher role in sustainability education and to critically reflect on ways to embed a holistic approach to Education for Sustainability in early childhood contexts.