This research examines the spillover effect of information about a brand’s corporate social responsibility (CSR) activity on competing brands’ evaluations. Two experimental studies show that receiving information about a brand’s CSR activity (vs. receiving descriptive information about a brand) has a negative effect on a competing brand’s evaluations among consumers with high product category knowledge. Decreased trustworthiness perceptions of other brands in the same product category drive this effect. However, the negative spillover of a brand’s CSR information to a competing brand disappears among consumers with low product category knowledge, or if a competing brand has low brand typicality. Together, this research allows a more nuanced understanding of the spillover effect of CSR information and offers managerial implications for the strategic use of CSR activities in brands’ marketing communications.