It is a perennial challenge for different political organisations, including environmental NGOs (ENGOs), to accommodate diverse social and political groups’ interests, opinions, and experiences. Without sufficient inclusiveness, ENGOs struggle to help create social and political change at a much faster pace, with climate action in Australia being a key example. In this regard, this paper argues that inclusiveness needs to encompass three dimensions, diversity, equity, and procedural justice, which are critical to managing internal tensions, disagreements, and conflicts. Evidence from two different ENGOs, the Australian Conservation Foundation (ACF) and Extinction Rebellion Australia (XR Aus), shows that despite different types of organisational structures and resource availability, there are different challenges and opportunities for the two ENGOs in trying to establish and maintain higher inclusiveness. While diversity remains challenging to both groups, XR Aus’s self-organising and decentralisation have much easier access to decision-making and autonomous participation than ACF. However, it remains to be seen if XR Aus could harass its organising features to establish and maintain a higher level of procedural justice. These findings are relevant not only to issues in climate action problems but also to other collective action problems such as ethnics equality, domestic violence, income disparity, and gun control.