This study was the first to test both the independent and additive effects of change-detection prompts and warnings about potential discrepancies between an event and post-event information on susceptibility to misinformation. Participants (N = 239) viewed a mock crime video, read a post-event narrative containing misinformation, and completed a memory test about the video content. Participants were randomly assigned to change-detection and warning conditions. Ecological validity was enhanced by describing the materials as a police training exercise and by examining effects of one versus four misinformation items (opposed to typically higher rates in experimental research). Using a novel statistical approach for this topic (GLMM), we compared across the misinformation quantities participants received. Change-detection prompts, but not a pre-warning, decreased misinformation rates, and the effect of change-detection was not enhanced by a pre-warning. Results held regardless of misinformation quantity. These findings emphasize the utility of change-detection mechanisms for increasing misinformation resistance.