After decades of research, we know that the mesolimbic dopamine pathway is heavily involved in nearly all aspects of financial decision-making. Its role has been defined by its involvement in reward-related learning as it relates to monetary gains. There is little evidence implicating it in aversive or loss-related learning. This dissertation was designed to advance our understanding of this systems involvement in aversive and loss related decision making. To do this, we use functional magnetic resonance imaging while human participants engage in experimental economic tasks that deal with financial decisions over gains and losses. We show that, 1) during decision-making, the ventral striatum tracks the expected values of gambles that are entirely aversive, 2) heterogeneity in loss-holding behavior in the stock market can be explained via activity within the ventral striatum, and 3) the ventral striatal processes earnings announcements which lead to financial loss, and are correlated with subsequent changes in stock price. We find that the BOLD response in the ventral striatum to loss outcomes in all three of our experiments fit with the prediction error hypothesis of dopamine activity. Finally, we discuss future research in financial loss, and its implications for sub-optimal behavior, such as gambling addiction.