Amidst mounting global crises spanning environmental, social, and economic domains, sustainability education has emerged as a vital pathway toward a thriving future. However, despite its promise, the concept of sustainability often remains superficial, leaving educators ill-equipped to address its complexities. While efforts to integrate sustainability into education are underway, critical pedagogy, a crucial tool for fostering social change, is notably absent from instructional practices. This action research project utilized critical pedagogy to design and implement a critical professional development (CPD) workshop within a larger fellowship program to center justice within sustainability in both content and pedagogical approach. As a result, participants’ definitions and understandings of sustainability increased across all measurements of extent, breadth, and depth. Specifically, participants redefined collaborative relationships and more prominently included notions of justice and equity in their conceptualizations of sustainability and sustainability education. The use of critical pedagogy encouraged teachers to analyze intersectional oppressive systems and fostered a new, critical perspective on sustainability. In their own educational designs, participants demonstrated an intention to model elements of critical pedagogy, such as dialogic action and permeable content. Finally, in alignment with the intended outcomes of CPD, participants developed cooperative space for co-learning, built unity, shared leadership, and felt confident implementing their own professional development to address context-specific concerns. By using critical pedagogy in sustainability education, the workshop participants prioritized deep and caring relationships which fostered empathic engagement with the intersectional and often dehumanizing systems that have led to interconnected global crises. The results indicated that using CPD as a framework could be effective in teacher professional development for sustainability as a design and implementation tool to center critical work that examines systemic issues of injustice and exploitation against both humans and our planet.