Studies have linked personality dispositions to important social evaluations, such as how much power individuals are granted, or how much they are liked. Yet, these links are not always consistent and seem to depend on the social context. We zeroed in on this issue, testing two mutually non-exclusive hypotheses on how the context might moderate the effects of personality dispositions on perceptions of power and likability in newly formed groups. The behavior contingency hypothesis posits that the context moderates the extent to which a disposition is expressed in behavior. The valuation contingency hypothesis posits that the context moderates the extent to which disposition-specific behavior is valued. In a round-robin study, we found support for both hypotheses with regard to perceptions of power (but not with regard to likability). The findings reveal the importance of behavior expression and valuation in the processes underlying personality-situation interactions in power hierarchies.