Narrative episodic memory of movie clips can be retroactively inhibited by presenting unrelated stimuli coinciding with event boundaries. This effect has been alternatively linked with rapid hippocampal processes related to memory consolidation and triggered by the offset of the event, or with working memory processes. Here we tested whether this effect extended to spatial memory, the temporal specificity and extent of interference and its effect on working- vs long-term memory. In three computerized adaptations of the Morris Water Maze participants learned the location of an invisible target over three trials each. A second spatial navigation task was presented either immediately after finding the target, after a 10-second delay, or no second task was presented (control condition). A recall session, in which participants indicated the learned target location with 10 ‘pin-drop’ trials for each condition, was performed after a 1-hour or a 24-hour break. Spatial memory was measured by the mean distance between pins and the true location. Results indicated that the immediate presentation of the second task led to worse memory performance, for both break durations, compared to the delayed condition. There was no difference in performance between the delayed presentation and the control condition. Despite this long-term memory effect, we found no difference in the rate of performance improvement during the learning session, indicating no effect of the second task on working memory. Our findings are in line with a rapid process, linked to the offset of an event, that is involved in the early stages of memory consolidation.