Celebrity endorsements are widely adopted as part of the marketing strategies for many brands, given celebrities can engage their fans to patronize the brand and to distribute celebrity-featuring promotion messages online. With the proliferation of the Internet, these fans may also defend their beloved celebrities when they are being attacked. However, whether a consumer’s positive attitude to the endorser would impact their behaviour toward the endorsed brand remains unclear. Qualitatively studying based on a few leading online communities, we explored the impact of attitude towards brand-endorsing celebrities on online consumers’ behaviour (likelihood of brand defending and purchase intention), which would foster the brand’s electronic word-of-mouth (eWOM). We also identified several endorsers’ traits that drive consumers’ attitudes towards brand-endorsing celebrities and the role of exposure frequency of celebrity-featured advertisements on consumers’ attitudes towards the endorsed brand.