Purpose: While past studies have shown that corporate social responsibility (CSR) influences brand equity, loyalty and brand attitudes, research about CSR effects on the responsible and active dimensions of brand personality remains limited. This study aims to address this gap and examine how brands with different personality strength benefit from CSR communication, providing novel insights about CSR’s branding payoffs to firms. Design/methodology/approach: Three experiments were conducted. Study 1 tested if CSR communication influenced responsible and active brand personality dimensions compared to non-CSR communication. Study 2 examined how varying CSR spending allocations affect personality perceptions of weak and strong brands. Studies 1 and 2 measured responsible and active brand personalities before and after exposure to experimental manipulations, assessing immediate changes in brand personality. Study 3 replicated the results of Study 2 using fictitious brands whose initial brand personalities were manipulated as either weak or strong. Findings: CSR communication has the potential to influence brands’ responsible and active personalities compared to non-CSR communication. However, changes in brand personalities were contingent on CSR manipulations (smaller vs larger CSR spending) and initial brand strength. Brands that lacked strongly responsible and strong active personalities experienced an improvement in these perceptions after exposure to any CSR spending message. However, brands with strong responsible or strong active personalities experienced brand erosion after exposure to smaller CSR spending message or no improvement when the CSR message was aligned with the responsible and active conduct (e.g. mentioned larger CSR spending). Originality/value: This study is the first to examine how CSR affects brand personality. By combining signalling and attitude change/congruity principle theories, it provides novel theoretical contributions to explain when CSR can improve, erode or exert no effect on the responsible and active brand personalities, providing insights for effective brand management.