While reminders can help by encouraging prosocial behaviors, we propose that they can also hurt. Across 10 studies, most of which focus on reminders to express gratitude, we find that reminders interfere with impressions of genuine prosociality. Whether people are reminded subtly (Studies 1a and 6-8) or blatantly (Studies 2-5) to express gratitude, the reminder is perceived to put social pressure on the potential thanker, making reminded thankers seem less genuine and less likable than spontaneous thankers. This is true from the perspective of both a third-party observer (Studies 1a and 2-7) and the receiver of thanks (Study 4), regardless of whether the judgments are about hypothetical (Studies 1a, 2-3, and 6-7) or real behavior (Studies 4-5). We find that this phenomenon can have material consequences: Receivers of gratitude expressions allocated a larger proportion of bonus money to a spontaneous thanker compared to a reminded thanker (Study 5). We also find that to overcome the decrement in their perceived genuineness, reminded thankers must engage in costly signaling by thanking more elaborately (Study 7), and reminded thankers spontaneously do this (Study 8). Overall, while reminding people to engage in prosocial actions may encourage laudable behavior (Study 6), our findings suggest that doing so may also undermine the actor's perceived genuineness, leading to material consequences and raising the bar for what is required to signal sincerity. (PsycInfo Database Record (c) 2024 APA, all rights reserved).