Mindfulness is a state of paying conscious and nonjudgmental attention to present‐moment experiences. Previous research relates this state to more effective emotion regulation and less emotion reactivity. We therefore hypothesized an attenuating effect of a mindfulness exercise on moral reactions that usually results from a bad conscience when having caused harm. Across five studies, we experimentally induced mindfulness via a short breathing exercise and then assessed harm‐based moral reactions. As hypothesized, participants in the mindfulness (vs. control) exercise condition showed (i) attenuated repair intentions after having read a scenario in which participants caused harm to a friend (Study 3) and (ii) attenuated intentions to change harm‐causing eating habits (Study 4). Results of Studies 1, 2 and 5 did not provide evidence for our hypothesis. A following meta‐analysis across all five studies yielded an overall significant effect of mindfulness in the harm‐condition, providing preliminary evidence for a potential downside to mindfulness.