Long-term synaptic plasticity involves changes in the expression and membrane insertion of cell-surface proteins. Interestingly, the mRNAs encoding many cell-surface proteins are localized to dendrites, but whether dendritic protein synthesis is required for activity-induced surface expression of specific proteins is unknown. Herein, we used microfluidic devices to demonstrate that dendritic protein synthesis is necessary for activity-induced insertion of GluN2A-containing NMDA receptors in rat hippocampal neurons. Furthermore, visualization of activity-induced local translation of GluN2A mRNA and membrane insertion of GluN2A protein in dendrites was directly observed and shown to depend on a 3' untranslated region cytoplasmic polyadenylation element and its associated translation complex. These findings uncover a novel mechanism for cytoplasmic polyadenylation element-mediated posttranscriptional regulation of GluN2A mRNA to control NMDA receptor surface expression during synaptic plasticity.