The roles of glial neurotransmitter receptor signalling in vivo remain a matter of some debate. Here, the authors generated mice in which AMPA glutamate receptors (AMPARs) could be conditionally knocked out in Bergmann glial cells, a type of cerebellar astrocyte. Loss of AMPARs led to glial process retraction from Purkinje cell spines, and young animals showed delayed glutamatergic synapse formation. Young and old mice also exhibited deficits in fine motor coordination, suggesting that Bergmann glial cell AMPARs are needed for proper cerebellum-mediated motor function.