The IT-mediated nature of e-commerce creates the uncertainty in online buyer-seller relationships where online buyers are difficult to personally scrutinize sellers, leading to many challenges for online sellers to win buyers’ trust. In order to overcome this problem, according to impression management theory and relationship theory, this research proposes a research framework for understanding how impression management tactics can be used by sellers to create a positive impression in the minds of buyers, affect buyers’ trust in the sellers, and subsequently purchase from them. This research further examines the moderating role of relationship norms on the relationship between impression management tactics and trust. A Web-based survey is then conducted in Yahoo! Taiwan auction to validate our proposed framework. Our research is expected to contribute to the theories by first examining the impression management theory and relationship theory in the context of online auctions. We also expect to contribute to the practice by illustrating that sellers should adjust their impression management tactics to suit buyers’ relationship norms. Specifically, self-focused tactics are more useful for buyers in an exchange relationship; other-focused tactics are more effective for buyers in a communal relationship.