Both ‘green’ (environmental) and ‘red’ (social justice) NGOs have started to use the language of climate justice in recent years as a banner for both advocacy and campaigns. Yet little is known about why climate justice has risen to prominence and there appears to be considerable diversity in how NGOs themselves frame the concept. In this context, this paper reports the results of the first half of a research project which is examining how NGOs in the UK and Australia conceptualize climate justice. Drawing on preliminary analysis of a series of key informant interviews conducted between November 2013 and January 2014, I examine what climate justice means to UK NGOs, how and why they engaged with it as a concept, and how it articulates with their policy, programmes and advocacy.