The prefrontal cortex (PFC) plays an important role in regulating anxiety–like phenotypes and social behaviors, and impairments in this brain region has been linked to social deficits in mammals. Childhood obesity is associated with an increased risk of neuropsychiatric behavioral abnormalities, including attenuated social preference and increased anxiety–like behaviors in adulthood. However, little data are available on the impact of obesity during adolescence on PFC–dependent behaviors. Herein, we use the mice pups to illuminate whether and how high–fat diet (HFD) feeding in adolescence affects medial prefrontal cortex (mPFC)–dependent behaviors, and what the underlying cellular and molecular mechanism is. We found that juvenile HFD feeding results in the accumulation of senescent astrocytes and microglia in the mPFC of mice. Furthermore, we found a causal link between the accumulation of senescent glial cells and HFD–induced neuropsychiatric behavioral abnormalities. Pharmacological clearance of senescent glial cells in HFD–fed mice enhances neuronal activity and reserves synaptic excitatory/inhibitory balance, thus preserving normal behaviors. Collectively, these results show that senescent glial cells play a significant role in the initiation and progression of juvenile obesity–mediated neuropsychiatric behavioral abnormalities, and suggest that targeting senescent glial cells may provide a therapeutic avenue for the treatment of obesity–related neuropsychiatric disorders in children.