How does one’s motivation to reach a desired conclusion influence whether or not they make illogical probability judgements? In this talk, I consider the conjunction fallacy as a test case for motivated reasoning, or the process of evaluating information in a way that coheres with prior attitudes and beliefs. In 3 studies, participants with prior motivations (e.g., fans of a sports team) made judgments about the likelihood of future events. People committed the conjunction fallacy consistent with a desirability bias: scenarios that included a desirable outcome were judged as more likely to happen when compared to less desirable scenarios, even if logically incoherent.