Glutamatergic synapses rely on AMPA receptors (AMPARs) for fast synaptic transmission and plasticity. AMPAR auxiliary proteins regulate receptor trafficking， and modulate receptor mobility and its biophysical properties. The AMPAR auxiliary protein Shisa7 (CKAMP59) has been shown to interact with AMPARs in artificial expression systems， but it is unknown whether Shisa7 has a functional role in glutamatergic synapses. We show that Shisa7 physically interacts with synaptic AMPARs in mouse hippocampus. gene deletion resulted in faster AMPAR currents in CA1 synapses， without affecting its synaptic expression. KO mice showed reduced initiation and maintenance of long-term potentiation of glutamatergic synapses. In line with this， KO mice showed a specific deficit in contextual fear memory， both short-term and long-term after conditioning， whereas auditory fear memory and anxiety-related behavior were normal. Thus， Shisa7 is a bona-fide AMPAR modulatory protein affecting channel kinetics of AMPARs， necessary for synaptic hippocampal plasticity， and memory recall.