BACKGROUND: The role of functional connectivity (FC) changes in the prefrontal-thalamic-cerebellar circuit in schizophrenia has received widespread attention. Currently, domestic and international studies on this circuit have focused on adults, while the FC of this circuit in the brains of adolescent patients with schizophrenia (AOS) has been less reported. METHODS: We recruited 124 subjects who underwent resting-state functional magnetic resonance imaging scans at baseline, using key brain regions in the prefrontal-thalamic-cerebellar circuit as seed regions, to investigate the FC in AOS versus healthy controls. The FC of this loop was compared with that of the whole brain in healthy controls. RESULTS: Compared to healthy controls, patients with AOS had reduced FC between the medial prefrontal cortex (mPFC) and precuneus (PCu) and between the posterior cerebellar lobe and middle temporal gyrus. Reduced FC between the left mPFC and the left PCu in patients with AOS was associated with positive symptom scores on the PANSS and was positively correlated with the Symbolic Encoding Scale, the Maze Scale, and the Category Fluency Test Scale. Reduced FC between the right posterior cerebellar lobe and the right middle temporal gyrus is positively correlated with the simple visuospatial memory test in AOS patients. CONCLUSIONS: There are FC abnormalities in the prefrontal-thalamic-cerebellar circuit, precuneus, and temporal lobe in AOS. These abnormalities appear in the early stages of schizophrenia, independent of medication, and are characteristic of the disorder.