The emerging field of neuroeconomics has provided evidence that emotional as well as cognitive processes may contribute to economic decision-making. Indeed, activation of the anterior insula, a brain area involved in emotional processing, has been shown to predict decision-making in the Ultimatum Game. However, as the insula has also been implicated in other brain functions, converging evidence on the role of emotion in the Ultimatum Game is needed. In the present study, 30 healthy undergraduate students played the Ultimatum Game while their skin conductance responses were measured as an autonomic index of affective state. The results revealed that skin conductance activity was higher for unfair offers and was associated with the rejection of unfair offers in the Ultimatum Game. Interestingly, this pattern was only observed for offers proposed by human conspecifics, but not for offers generated by computers. This provides direct support for economic models that acknowledge the role of emotional brain systems in everyday decision-making.