Intrusions, for example the flashback of a traumatic event, are a core symptom of psychological disorders, such as posttraumatic stress disorder (PTSD). Clinical populations report intrusions that are more vivid, causing distress and persistence of symptoms. Prior research suggests that the ability to generate vivid mental imagery is associated with vivid intrusions, while cognitive models, including the Self-Regulatory Executive Function (S-REF) and the cognitive model of PTSD, propose a mediating role for metacognitive beliefs. The present study examined whether mental imagery is associated with intrusion vividness and whether this relationship is mediated by metacognitive beliefs in a non-clinical sample. Stressor-related intrusions were induced using a trauma film paradigm and assessed over 24 hours. The results suggest that intrusion vividness shortly after stressor exposure is primarily driven by mental imagery whereas metacognitive beliefs may play a more prominent role in the maintenance of intrusions over time.