Contributions in the public goods game—a classical social dilemma situation—have been shown to depend strongly on the presence versus absence of punishment or sanctions for free riders. Also, there appear to be noteworthy individual differences in the degree to which decision makers cooperate. Herein, we aimed to bring these two lines of research together. Firstly, we predicted that both presence of punishment and high dispositional Honesty–Humility (as conceptualized in the Honesty–Humility, Emotionality, eXtraversion, Agreeableness, Conscientiousness, Openness to experience model of personality) should yield higher contributions. Secondly, and more importantly, we expected an interaction, such that only those low in Honesty–Humility would condition their behaviour on the presence versus absence of punishment, thus employing cooperation strategically. In line with the hypothesis, the results of two experiments (one of which comprised a longitudinal design) corroborated that the degree to which decision makers shift towards higher contributions when punishment is introduced depends on their dispositional level of Honesty–Humility. Copyright © 2011 John Wiley & Sons, Ltd.