The misinformation effect refers to the distortion of memory reports about an event caused by misinformation presented to subjects concerning this event. It was hypothesized that mental warm-up would reduce vulnerability to misinformation but mental fatigue would enhance it, because mental warm-up would improve the memory of the original event, whereas mental fatigue would weaken it. This hypothesis was confirmed by three experiments in which participants were presented with an original event, read a description of that event, which in the experimental group contained details that were incongruent with the original event, and finally answered questions about the original event. It was also found that self-reference, both direct and indirect, defined as a personal connection with the case, alleviated the negative effects of fatigue and enhanced those of warm-up. The importance of the results for understanding the misinformation effect, as well as for applied forensic psychology, is highlighted.