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Background: Intrusive memories form a core symptom of Posttraumatic Stress Disorder (PTSD). Based on concepts of visuospatial interference and memory-updating accounts, technological innovations aim to attenuate such intrusions using visuospatial interventions. Objective: This study aims to test the effect of a visuospatial Tetris-based intervention versus a verbal condition (Wiki) and a never-targeted control (no intervention) on intrusion frequency. Method: A randomized crossover trial was conducted including N = 38 PTSD patients who had at least 3 distinct intrusive memories of trauma. After both 2 weeks (intervention 1) and 4 weeks (intervention 2), one of the three memories was randomly selected and either the visuospatial intervention (memory reminder of a traumatic memory + Tetris) or verbal condition (reading a Wikipedia article + answering questions) was performed on their first memory in randomized order. In the week 4 session, the patient conducted the other intervention condition on their second memory (crossover). The third memory was never targeted (no intervention). Daily occurrence of intrusions over 8 weeks was collected using a diary and analysed using mixed Poisson regression models. Results: Overall, there was no significant reduction in intrusion frequency from either intervention compared to each other, and to no intervention control (relative risk Tetris/Wiki: 0.947; p = .31; relative risk no intervention/Tetris: 1.060; p = .15; relative risk no intervention/Wiki: 1.004; p = .92). Conclusions: There was no effect of either intervention on intrusions when administered in a crossover design where participants received both interventions. Design shortcomings and consequences for future studies are discussed.