Significance Learning predefined sequences of actions is of everyday importance. Recent evidence suggests that improvements in performance associated with learning a motor sequence take place during the quiet rest periods interleaved with practice. This phenomenon known as micro-offline gains (MOGs) is different from offline gains in performance observed overnight. Using a multimodal—functional and structural—MRI approach, here we show that the hippocampus participates in the generation of MOGs through a mechanism reminiscent of memory reactivation. Our findings point to the involvement of the hippocampus in the reactivation of nonhippocampal memories and provide evidence for a possible common mechanism at the basis of the formation of declarative and nondeclarative memories.