Climate activism has risen in recent years. Some movements (e.g., Extinction Rebellion) have adopted radical strategies (e.g., civil disobedience) to raise awareness and demand policy action. However, these actions often face criticism due to perceived threats and moral violations. Our research aims to explore how understanding the motivations of the activists can enhance people’s identification with the movement and its moral goals, and increase the perception of climate change injustice, fostering engagement in collective actions related to the cause. Using the Social Identity Model of Collective Action (SIMCA), we will investigate whether exposure to activists’ motivations (i.e., movement’s manifesto) before exposure to their actions can influence people’s evaluations of climate change-related collective actions and encourage activism. We will conduct an online multi-national study to gain insights into environmental collective actions. Ultimately, our findings may help environmental movements develop more effective strategies to mobilize people for climate action.