AbstractTo reduce environmental problems, citizens, governments, and organisations need to take action to reduce their environmental impact. In the current paper, we tested if and how perceived environmental responsibility of organisations and government is related to pro-environmental behaviour and acceptability of pro-environmental policies among employees, customers, and citizens. We hypothesised that the stronger perceived environmental responsibility of organisations and government, the stronger the environmental self-identity of employees, customers, and citizens because they are a part of that organisation. We hypothesised that a stronger environmental self-identity, in turn, is positively related to a range of pro-environmental actions as well as acceptability of pro-environmental policies. We tested our hypotheses in three studies. We found that a stronger perceived environmental responsibility of organisations is indeed related to a stronger environmental self-identity among employees and customers of the organisation. A stronger environmental self-identity was in turn related to a range of pro-environmental actions. An alternative explanation for our findings is that those with a stronger environmental self-identity are more likely to become a customer at an organisation with a strong perceived environmental responsibility. However, we found support for our hypotheses among those who chose and among those who did not freely choose to be a customer of the organisation, suggesting that the alternative explanation does not fully explain our findings. Furthermore, we found that citizens report a stronger environmental self-identity when perceived environmental responsibility of their government is stronger. A stronger environmental self-identity was in turn related to a higher acceptability of policies aiming to promote energy savings. Our findings are in line with social identity theory, which states that people partly infer how they see themselves based on the groups to which they belong. Furthermore, our findings have important practical implications for organisations and governments aiming to promote pro-environmental behaviour. Specifically, if organisations and government reduce their environmental impact and clearly communicate this, citizens, employees, and customers may also be more likely to do so.