I introduce the construct of threat regulation as an agentic interpersonal process for building and maintaining trust. I examine threat regulation as a specific dimension of interpersonal emotion management that fosters trust and effective cooperation by allowing individuals to understand and mitigate the harm that their counterparts associate with cooperating—in particular, harm from opportunism, identity damage, and neglect of their interests. To explicate the microprocesses of threat regulation, I draw on social cognitive theory, symbolic interactionism, and the psychology of emotion regulation.