Cause-related marketing (CRM) is an increasingly popular corporate tactic, used to achieve sales promotion objective while supporting social causes. Originally, it was practised offline, and academic research on CRM has focused on that context (Ha 2008; Segev et al. 2014). However, the online medium presents unique characteristics, such as interactivity and global access, which influence marketing. Advances in digital technology and e-commerce innovations enable online marketers to target charity site visitors with their products through affiliated cause marketing (ACM) and cause- sponsorship (CS) advertisement tactics which are forms of online CRM. Typically, firms communicate an offer through an explicit donation to the charity in question, contingent on purchases made via a banner advertisement linked from the brand’s site (ACM ad format), or make a declaration of the brand's association with the charity (CS ad format). In light of this, this study investigates the impact of the main design features of the two typical forms of advertisers’ banner advert on charity websites by asking: I. Whether and how the donation amount in an ACM ad format influences consumers’ response regarding purchase intention. II. Whether and how the ad context congruence in a CS ad format influences consumers’ response regarding purchase intention. III. Do consumers respond more positively towards an ACM ad than a CS ad regarding attitudes and purchase intentions? The study uses a web-based experimental-survey design, with 538 UK national representative panel participants to generate field data. It examines this data using ANOVA and structural equation modelling (SEM) techniques. The main findings: i) support the hypothesised positive direct effects of donation amount (with respect to ACM ad format) and ad-context congruence (with respect to CS adformat) on consumers’ purchase intention; ii) the media effect in CRM demonstrates the serial mediating roles of ‘attitudes towards the ad’ and ‘perceived CSR motive of firm’ of the donation amount-purchase intention link, while ‘attitudes towards the ad’ mediates the ad-context congruence and purchase intention link; iii) charity cause involvement moderates the positive link of ad-context congruence to purchase intention; iv) attitude towards CS is found to be stronger than ACM with small donation; and iv) purchase intention towards the ACM ad formats is stronger than towards the CS ad format. The study makes theoretical and practical contributions by identifying composite models of consumers’ response towards ACM and CS tactics, with more favourable purchase intention towards ACM than CS