Memory traces of long-term auditory fear memories are stored in the auditory cortex. Perineuronal nets (PNNs) are stable components of the extracellular matrix that could potentially provide a scaffold for long-term synaptic plasticity. In a model of auditory fear conditioning, mRNAs encoding three lecticans — key components of PNNs — were increased in the auditory cortex. By contrast, enzymatic degradation of PNNs impaired fear learning, which recovered on regrowth of PNNs, suggesting that PNNs in auditory cortex are necessary for the consolidation of fear memories.