BACKGROUND: Administration of olanzapine (OLA) is closely associated with obesity and glycolipid abnormalities in patients with schizophrenia (SCZ), although the exact molecular mechanisms remain elusive. OBJECTIVE: We conducted comprehensive animal and molecular experiments to elucidate the mechanisms underlying OLA-induced weight gain. METHODS: We investigated the mechanisms of OLA-induced adipogenesis and lipid storage by employing a real-time ATP production rate assay, glucose uptake test, and reactive oxygen species (ROS) detection in 3T3-L1 cells and AMSCs. Rodent models were treated with OLA using various intervention durations, dietary patterns (normal diets/western diets), and drug doses. We assessed body weight, epididymal and liver fat levels, and metabolic markers in both male and female mice. RESULTS: OLA accelerates adipogenesis by directly activating glycolysis and its downstream PI3K signaling pathway in differentiated adipocytes. OLA promotes glucose uptake in differentiated 3T3-L1 preadipocytes. In mouse models with normal glycolipid metabolism, OLA administration failed to increase food intake and weight gain despite elevated GAPDH expression, a marker related to glycolysis and PI3K-AKT. This supports the notion that glycolysis plays a significant role in OLA-induced metabolic dysfunction. CONCLUSION: OLA induces glycolysis and activates the downstream PI3K-AKT signaling pathway, thereby promoting adipogenesis.