Across the domains of spatial navigation and episodic memory, the hippocampus is thought to play a critical role in forming distinct representations of overlapping events. However, it is less clear how and when hippocampal representations of overlapping events become distinct. Here, using spatiotemporal pattern analysis of human fMRI data, we measured learning-related changes in hippocampal representations of overlapping real-world routes. We found that learning resulted in highly targeted representational changes within the hippocampus that specifically reduced similarity among overlapping routes. Strikingly, and in contrast to representations in other navigation-related brain regions, hippocampal representations of overlapping routes diverged to the point where overlapping routes became less similar than non-overlapping routes. This learning-related plasticity preferentially occurred for hippocampal voxels that were initially shared across overlapping routes. Collectively, these findings indicate that overlap among event representations triggers a divergence of hippocampal activity patterns that dramatically reshapes representational structure.