Benzodiazepines (BZDs) are critical sedative, anticonvulsant, and anxiolytic drugs that potentiate inhibitory GABAergic neurotransmission. However, clinical utility is hampered by drug tolerance and a hyperexcitable withdrawal syndrome characterized by neuronal excitation/inhibition (E/I) imbalance. Although enhanced excitation is implicated in BZD tolerance, the homeostatic changes to glutamatergic receptors remain undefined. Here, we report the impact of chronic (7-day) BZD treatment on excitatory synapse and NMDA receptor (NMDAR) function, expression, and subcellular localization in cortical neurons. Chronic treatment with the BZD diazepam (DZP) resulted in an increase in NMDAR-mediated miniature excitatory postsynaptic currents (mEPSCs). Confocal imaging studies revealed a DZP-induced enrichment of GluN2B-containing NMDARs at functional synapses (expressing AMPA receptors, AMPARs) while GluN2B subunit expression was otherwise unaltered. Conversely, localization of GluN2A-containing NMDARs (GluN2A-NMDARs) to functional synapses was unchanged, while GluN2A-NMDAR total protein levels and surface accumulation were enhanced. Intriguingly, we demonstrate for the first time the BZD-induced enrichment and expansion of GluN2A-NMDAR coverage at silent (AMPAR-lacking) synapses. Finally, biochemical fractionation analysis of the translation elongation protein eEF2, known to control E/I balance, detected lower levels of deactivated, phosphorylated eEF2 in the synaptic fraction of DZP-treated neurons, indicative of enhanced local translation. Collectively, our findings suggest that chronic BZD treatment triggers compensatory mechanisms which 1) enhance NMDAR function via increased GluN2B-NMDARs at functional synapses, and 2) promote the expression, surface localization, and accumulation of GluN2A-NMDARs at silent synapses, augmenting the potential for further synaptic plasticity.