This experiment explores the effects of agency assignment and self-construal on responses to tornado preparedness messages. Participants (N = 276) were randomly assigned to one of four conditions crossing agency assignment and self-construal. Results found threat agency associated with greater perceived susceptibility and tornado threat, whereas self-construal was primarily associated with perceived threat severity, such that those primed with interdependent self-construal showed marginally increased perceptions of tornado severity relative to those primed with independent self-construal. Self-construal did not appear to moderate the effects of agency assignment on attitudes or behavioral intentions. Results are discussed in light of potential psychological reactance, suggesting human agency assignment should be used cautiously, since it may pose an increased threat to perceived freedoms in certain instances. Moreover, combining human agency and independent self-construal may trigger negative cognitions directed toward the message and/or its source. It is concluded that cautious, strategic use of agency assignment can improve message acceptance and facilitate adaptive, preparedness actions.