Purpose Companies are increasingly incorporating support for social causes in advertising to improve brand image and increase sales, but it is unclear how these behaviours influence purchase intentions. This paper aims to analyse this relationship from a strategic perspective to assess whether the degree of fit of any of the five strategic dimensions that Zdravkovic et al. (2010) propose influence purchase intentions synergistically. Design/methodology/approach This study includes two stages: a qualitative stage to build brand–cause relationships and a quantitative study of one of these relationships to examine which fit dimensions are involved and whether they generate synergy in purchase intentions. Findings Results demonstrate that adjustment to two of the five dimensions is sufficient to influence emotional responses positively. Research limitations/implications This study presents limitations, as it has been developed using a particular sample of university students. Practical implications These analyses provide tools for managers to verify which types of strategic fit operate in this relationship and facilitate co-branding planning to achieve financial goals. Originality/value The analysis provides tools for managers to verify which types of strategic fit operate in this relationship and facilitate co-branding planning to achieve financial goals.