AMPAR (α‐amino‐3‐hydroxy‐5‐methyl‐isoxazole‐4‐propionic acid receptor) is an ion channel involved in the formation of synaptic plasticity. However, the molecular mechanism that couples plasticity stimuli to the trafficking of postsynaptic AMPAR remains poorly understood. Here, we show that PIKE (phosphoinositide 3‐kinase enhancer) GTPases regulate neuronal AMPAR activity by promoting GluA2/GRIP1 association. PIKE‐L directly interacts with both GluA2 and GRIP1 and forms a tertiary complex upon glycine‐induced NMDA receptor activation. PIKE‐L is also essential for glycine‐induced GluA2‐associated PI3K activation. Genetic ablation of PIKE (PIKE−/−) in neurons suppresses GluA2‐associated PI3K activation, therefore inhibiting the subsequent surface expression of GluA2 and the formation of long‐term potentiation. Our findings suggest that PIKE‐L is a critical factor in controlling synaptic AMPAR insertion.