Memory distortions sometimes serve a purpose: It may be in our interest to misremember some details of an event or to forget others altogether. The present work examines whether a similar phenomenon occurs for source attribution. Given that the source of a memory provides information about the accuracy of its content, people may be biased toward source attributions that are consistent with desired accuracy. In Experiment 1, participants read desirable and undesirable predictions made by sources differing in their a priori reliability and showed a wishful thinking bias--that is, a bias to attribute desirable predictions to the reliable source and undesirable predictions to the unreliable source. Experiment 2 showed that this wishful thinking effect depends on retrieval processes. Experiment 3 showed that under some circumstances, wishes concerning one event can produce systematic source memory errors for others.