We frequently trust others—even strangers—based on little more than the good word of a third party. The purpose of this paper is to explain how such trust is possible by way of certain speech acts. I argue that the speech act of vouching is the primary mechanism at work in many of these cases and provide an account of vouching in comparison to the speech act of guaranteeing. On this account, guaranteeing and vouching both commit the speaker to certain actions conditional on undesirable events. However, while guaranteeing may generate reliance in someone or something by providing insurance against bad outcomes, vouching may generate trust in another agent by way of the vouching party manifesting their own trust in the party vouched for and enjoining the addressee to trust likewise.