Previous research suggests that people form impressions of others based on their facial appearance in a very fast and automatic manner, and this especially holds for trustworthiness. However, as yet, this process has been investigated mostly in a social vacuum without taking interpersonal factors into account. In the current research, we demonstrate that both the relationship context that is salient at the moment of an interaction and the performed behavior are important moderators of the impact of facial cues on impression formation. It is shown that, when the behavior of a person we encounter is ambiguous in terms of trustworthiness, the relationship most salient at that moment is of crucial impact on whether and how we incorporate facial cues communicating (un)trustworthiness in our final evaluations. Ironically, this can result in less positive evaluations of interaction partners with a trustworthy face compared to interaction partners with an untrustworthy face. Implications for research on facial characteristics, trust, and relationship theories are discussed. Copyright © 2008 John Wiley & Sons, Ltd.