Previous research has found that negative-valence appeals relating to the self (Don’t be a cheater) are more effective at reducing unethical behaviour than appeals relating to behaviour (Don’t cheat). We aimed to replicate these findings and examine whether positive-valence appeals relating to the self (Be an honest person) and to behaviour (Answer honestly) could have a similar effect. We ran five experiments with Israeli and U.S. samples, using social interaction and anonymous settings, and different methodologies: Die roll, coin-flip and number choice. A meta-analysis of the five experiments revealed a small effect of the self-appeals relative to the behaviour-appeals. These findings provide additional support for the theoretical explanation offered in terms of the role of the self in regulating unethical behaviour. However, the effect sizes found in our experiments were smaller than the ones previously reported. We discuss the merit in using self-appeals to reduce unethical behaviour, the possible advantage of positive-valence self-appeals, and the possible moderating role of the setting in which the behaviour takes place: Social interaction versus anonymous settings.