Parkinson’s disease (PD) is one of the most prevalent neurodegenerative diseases and disease-modifying treatment is required to inhibit the disease progression. We have previously reported that 8-OH-DPAT, serotonin (5-HT)1A full agonist, induced expression of antioxidant metallothionein (MT) in astrocyte and exhibited protective effects against 6-OHDA-induced neurodegeneration of nigrostriatal dopamine (DA) neuron. In this study, we investigated neuroprotective effect of anti-depressant mirtazapine, as an indirect 5-HT1A agonist, against dopaminergic neuronal death. Mirtazapine administration to 6-OHDA-injected hemi-parkinsonian mice significantly increased MT expression in striatal astrocytes and inhibited the reduction of nigrostriatal DA neuron. These effects were cancelled by simultaneous administration of 5-HT1A antagonist. To explore the precise neuroprotective mechanism, we examined effects of mirtazapine using primary cultured mesencephalic neurons and striatal astrocytes from rat fetus. Neuroprotection by mirtazapine was observed only in neuron-astrocyte co-cultured condition. Furthermore, MT expression in astrocyte was significantly increased when astrocytes were treated with mirtazapine-pretreated neuronal conditioned medium (Mir-NCM). Treatment with medium from Mir-NCM-treated astrocytes (Mir-NCM-ACM) showed dopaminergic protection against 6-OHDA. These effects were cancelled when astrocytes were treated Mir-NCM and 5-HT1A antagonist. Moreover, MT antibody completely cancelled the neuroprotective effects of Mir-NCM-ACM. These results suggested that mirtazapine protected DA neurons by inducing expression and secretion in/from astrocytes via indirect stimulation on astrocytic 5-HT1A receptor.