Recent dual-process models of decision making have suggested that emotion plays an important role in decision making; however, the impact of incidental moods (i.e., emotions unrelated to the immediate situation) on decisions remains poorly explored. This question was investigated by inducing 2 basic emotional states (amusement or sadness) that were compared with a neutral-emotion control group. Decision making was assessed with a well-studied social task, the Ultimatum Game. In this task, participants had to make decisions to either accept or reject monetary offers from other players, offers that varied in their degree of unfairness. Emotion was induced with short movie clips. Induced sadness interacted with offer fairness, with higher sadness resulting in lower acceptance rates of unfair offers. Induced amusement was not associated with any significant biases in decision making. These results demonstrate that even subtle incidental moods can play an important role in biasing decision making. Implications of these results in regards to the emotion, cognitive neuroscience, and clinical literatures are discussed.