Scholars have noted that face-to-face (FTF) interaction promotes honesty because it provides opportunities for conversation in which parties exchange information and build rapport. However, it is unclear whether FTF interaction promotes honesty even in the absence of opportunities for back-and-forth conversation. We hypothesized a minimal interaction effect whereby FTF interaction promotes honesty by increasing potential deceivers’ consideration of their own moral-interest. Using a modified version of the deception game (Gneezy, 2005), we held constant information exchange and manipulated whether it was delivered via a restricted FTF interaction or anonymously. In support of our hypothesis, the minimal FTF interaction increased honesty relative to an anonymous interaction. This effect was mediated by the greater activation of potential deceivers’ moral-interest under FTF interaction than under anonymity. We also ruled out alternate accounts involving interpersonal liking, expected counterpart trust, and retaliation fear as honesty-promoting mechanisms.