This paper seeks to examine how Australian environmental non-governmental organisations (ENGOs) communicate about and mobilise their supporters for climate justice. ENGOs play an important role in raising awareness and changing values, attitudes and behaviours related to climate justice. However, while a number of Australian ENGOs have begun incorporating language around climate justice in their communications, it remains unclear how they are conceptualised and enacted. Using data collected from 619 ENGO websites and 149 grant applications, we examine how ENGOs describe climate justice and the collective action frames they use to mobilise action. We found that while few ENGOs provided detailed explanations of climate justice on their websites, they primarily frame climate injustice as a procedural and distributive problem. The fossil fuel sector was most commonly identified as the cause of climate injustice, and First Nations communities most commonly affected. ENGOS consistently linked specific climate justice dimensions to relevant issues and solutions, suggesting a sophisticated understanding of how climate justice can be enacted. However, they primarily proposed incremental tactics involving education, solidarity and allyship behaviours, rather than radical actions through which to drive a transformative agenda of social, political or economic change. We conclude the paper with a discussion of applied implications for ENGOs and suggestions for future research.