This study examined the impact of brand familiarity and endorsers’ congruence with product being advertised on consumer responses to social media advertising in Twitter. Findings suggested that the product with a familiar brand endorsed by celebrity with high image congruence led to greater consumer trust, more positive attitude, and greater purchase intention than any other familiarity-congruence combinations. Interestingly, for unfamiliar brand, there is no significant difference between high and low endorsers’ congruence.