Norm violations can be contagious. Previous research analyzed two mechanisms of why knowledge about others’ norm violations triggers its spread: (1) Actors lower their subjective beliefs about the probability or severity of punishment, or (2) they condition their compliance on others’ compliance. While earlier field studies could hardly disentangle both effects, we use a laboratory experiment which eliminates any punishment threat. Subjects (n = 466) can throw a die and are paid according to their reported number. Our design rules out any possibility of personal identification so that subjects can lie about their thrown number and claim inflated payoffs without risking detection. The aggregate distribution of reported payoffs allows the estimation of the extent to which the honesty norm is violated. We compare two treatment conditions in which subjects are informed about lying behavior of others with a control condition without information feedback. Observations from a subsequent die throw reveal that knowledge about liars triggers the spread of lying compared to the control condition. Our results demonstrate the contagiousness of norm violations, where actors imitate norm violations of others under the exclusion of strategic motives.