Although honesty is typically conceptualized as a virtue, it often conflicts with other equally important moral values, such as avoiding interpersonal harm. In the present research, we explore when and why honesty enables helpful versus harmful behavior. Across 5 incentive-compatible experiments in the context of advice-giving and economic games, we document four central results. First, honesty enables selfish harm: people are more likely to engage in and justify selfish behavior when selfishness is associated with honesty than when it is not. Second, people are selectively honest: people are more likely to be honest when honesty is associated with selfishness than when honesty is associated with altruism. Third, these effects are more consistent with genuine, rather than motivated, preferences for honesty. Fourth, even when individuals have no selfish incentive to be honest, honesty can lead to interpersonal harm because people avoid information about how their honest behavior affects others. This research unearths new insights on the mechanisms underlying moral choice, and consequently, the contexts in which moral principles are a force of good versus a force of evil. (PsycInfo Database Record (c) 2021 APA, all rights reserved).