This chapter explores the relationships between justice and sustainability theory and argues that despite being entwined, practical and theoretical challenges prevent an easy or complete integration of these two concepts. Specifically, we examine how the multiscalar, multigenerational, and multidimensional characteristics of sustainability interact with ideas of just processes or just outcomes. Using insights from justice theory, sustainability science, and the social psychology of justice, we suggest we ask questions like: what would a just multiscalar and multigenerational sustainability process look like? If social context changes how people use or understand ideas of justice, what should justice look like in complex sustainability challenges that extend across traditional boundaries? We suggest that although these issues present persistent theoretical challenges, past and ongoing efforts – such as environmental justice work or international climate negotiations – provide some lessons and guidance about strategies for assisting this integration in practice. Overall this chapter suggests that although fully integrating justice and sustainability may not be entirely possible, sustainability without a consideration of justice would be nonsensical from a normative perspective and difficult to achieve strategically. This leaves us with a strong rationale to insist on the centrality of justice in any sustainability effort, but with an awareness of the complexities of doing so.