In this study, we tested the somatic marker hypothesis (SMH) by using an adaptation of the Iowa Gambling Task (IGT) in which the emotional context associated with primary inducers was systematically manipulated. In this modified version of the IGT, a picture of either a happy face or a fearful face was presented after each feedback. Critically, the expression of the face was either congruent or incongruent with the feedback delivered. Analyses of participants' choices revealed that the congruency of the emotional context with the feedback affects performance on the IGT: The ability to choose advantageously increases when the emotional context is congruent with feedback (i.e., happy faces after rewards and fearful ones after punishments), whereas this ability is impaired with an incongruent emotional context (i.e., fearful faces after rewards and happy faces after punishments). These findings provide evidence that decision making under ambiguity is driven by emotion-related signals, as postulated by the SMH.