The present research examined the interplay of individual differences in self-regulatory mechanisms as outlined in regulatory focus theory (promotion- and prevention-focus) and a cue of being watched in the context of cooperative behaviour. Study 1 revealed that the more individuals' habitual self-regulatory orientation is dominated by a vigilant prevention focus, the more likely they are to act cooperatively (i.e. to donate money to natural conservation organizations) when a subtle cue of being watched renders reputational concerns salient. In contrast, when no such cue is provided individuals' habitual vigilant self-regulatory orientation is negatively related to cooperative behaviour. Study 2 replicated the results of the initial study and examined interpersonal sensitivity (empathic concern) as a potential mediator of the observed effects. Copyright © 2010 John Wiley & Sons, Ltd.