Stakeholders increasingly expect firms to consider their social and environmental impacts as well as their economic impacts, and address their corporate social responsibility (CSR). One stakeholder group, consumers, report they want to be informed of how firms do this, and use this information when purchasing. This paper reports on an investigation of two message variables believed necessary for effective advertising about CSR initiatives, social topic information and social impact specificity. We manipulated each of these variables at three levels for an unfamiliar retail bank brand engaging with the social issue of the arms trade. While social topic information was found to be non-significant in influencing the dependent variable, overall scepticism toward CSR claims, social impact specificity was found to have a significant link to message inhibition of scepticism cognitions. The findings are insightful for marketing communications managers tasked with effectively informing a key stakeholder audience, consumers, of a firm’s pro-social achievements.