Damaged mitochondria can be released from neurons for uptake by glia for disposal. In this study, however, exposure of mice to focal cerebral ischaemia resulted in the release of functional mitochondria from astrocytes and their uptake into adjacent neurons, and these events were coincident with upregulation of the enzyme CD38 in astrocytes. Downregulation of this enzyme in astrocytes reduced both the number of astrocyte-derived mitochondria produced in response to ischaemia and their neuronal uptake. Ischaemia-induced neurological deficits were also increased, suggesting that these mitochondria are neuroprotective.