Uncertainty and emotion are an inevitable part of everyday life and play a vital role in mental health. Yet, our understanding of how uncertainty and emotion interact is limited. Here, an online survey was conducted (n = 231) to examine the whether uncertainty evokes and modulates a range of negative and positive emotions. The data show that uncertainty is predominantly associated with negative emotional states such as fear/anxiety. However, uncertainty was also found to modulate a variety of other negative (i.e. sadness/upset, anger/frustration, confusion) and positive (i.e. surprise/interest and excited/enthusiastic) emotional states, depending on the valence of an anticipated outcome (i.e. negative, positive) and the sub parameter of uncertainty (i.e. risk and ambiguity). Uncertainty increased the intensity of negative emotional states and decreased the intensity of positive emotional states. These findings support prior research suggesting that uncertainty is aversive and associate