Neurodevelopmental disorders are marked by inappropriate synaptic connectivity early in life, but how disruption of experience-dependent plasticity contributes to cognitive and behavioural decline in adulthood is unclear. Here we show that pup gathering behaviour and associated auditory cortical plasticity are impaired in female Mecp2^het mice, a model of Rett syndrome. In response to learned maternal experience, Mecp2^het females exhibited transient changes to cortical inhibitory networks typically associated with limited plasticity. Averting these changes in Mecp2^het through genetic or pharmacological manipulations targeting the GABAergic network restored gathering behaviour. We propose that pup gathering learning triggers a transient epoch of inhibitory plasticity in auditory cortex that is dysregulated in Mecp2^het. In this window of heightened sensitivity to sensory and social cues, Mecp2 mutations suppress adult plasticity independently from their effects on early development.