As the global prevalence of exposure to traumatic events rises, there is a growing need for accessible and scalable treatments for trauma-related disorders like posttraumatic stress disorder (PTSD). Intrusive reexperiencing symptoms, such as trauma-related intrusive memories (TR-IMs), are central to PTSD and a target of gold-standard treatments that are effective but resource-intensive. This study examined whether completing a brief ecological momentary assessment (EMA) protocol assessing the occurrence and phenomenology of TR-IMs was associated with decreases in intrusion symptom severity. Trauma-exposed adults (N = 139) experiencing at least 2 TR-IMs per week related to a DSM-5 criterion A traumatic event completed a 2-week EMA protocol. During this period, they reported on 18 sensory-perceptual and affective qualities of their TR-IMs three times per day and on posttraumatic stress symptom severity at day’s end. Longitudinal symptom measurements were entered into linear mixed-effects models to test the effect of Time on symptom severity. Over the 2-week protocol, intrusion symptom severity decreased, while other symptom cluster scores did not change. Within the intrusion symptoms, this effect was specific to TR-IMs and emotional reactivity to trauma reminders, and was not moderated by survey completion rate, total PTSD symptom severity, ongoing treatment, or time since trauma. This study was quasi-experimental and lacked a control group, therefore no definitive conclusions about clinical utility can be made. Nonetheless, these findings provide preliminary proof-of-principle and warrant future clinical trials assessing the clinical efficacy of EMAs of intrusive trauma memories as a scalable treatment option targeting intrusive memory symptoms.