Pandey, Bessières, et al. report that Igf2 expression in hippocampal pericytes, but not neurons, astrocytes, microglia, endothelial cells, or fibroblasts, is increased by learning and required for long-term memory. Pericytic Igf2 expression is driven by neuronal activity and controls neuronal mechanisms. Thus, pericyte-neuron cooperation plays a key role in memory.