Climate change is a global problem requiring a collective response. Grassroots advocacy has been an important element in propelling this collective response, often through the mechanism of campaigns. However, it is not clear whether the climate change campaigns organized by the environmental advocacy groups are successful in achieving their goals, nor the degree to which other benefits may accrue to groups who run them. To investigate this further, we report a case study of the Australian climate change advocacy sector. Three methods were used to gather data to inform this case study: content analysis of climate change organizations’ websites, analysis of website text relating to campaign outcomes, and interviews with climate change campaigners. Findings demonstrate that climate change advocacy is diverse and achieving substantial successes such as the development of climate change-related legislation and divestment commitments from a range of organizations. The data also highlights additional benefits of campaigning such as gaining access to political power and increasing groups’ financial and volunteer resources. The successful outcomes of campaigns were influenced by the ability of groups to sustain strong personal support networks, use skills and resources available across the wider environmental advocacy network, and form consensus around shared strategic values. Communicating the successes of climate change advocacy could help mobilize collective action to address climate change. As such, this case study of the Australian climate change movement is relevant for both academics focusing on social movements and collective action and advocacy-focused practitioners, philanthropists, and non-governmental organizations.