With the elderly population rapidly growing, the prevalence of Parkinson’s disease (PD) is quickly increasing because neurodegenerative disorders are usually late-onset. Herbal medicines and formula are adjuvant therapies of conventional PD agents, which result in serious side effects with long-term use. This study evaluated the neuroprotective effects of DA-9805, a standardized herbal formula that consists of an ethanolic extract of Moutan Cortex Radix, Angelica Dahuricae Radix, and Bupleuri Radix against 6-hydroxydopamine (6-OHDA)-induced cytotoxicity in vitro and in vivo. In PC12 cells, DA-9805 at concentrations of 1 and 10 μg/mL ameliorated cell viability, which was reduced by 6-OHDA. In addition, DA-9805 activated the extracellular-regulated kinase-nuclear transcription factor-erythroid 2-related factor 2 pathway, subsequently stimulating antioxidative enzymes such as NAD(P)H:quinone oxidoreductase 1 and catalase and suppressing apoptosis. Furthermore, DA-9805 prevented 6-OHDA-induced movement impairment, as well as a decrease of dopaminergic neurons and dopamine transmission in rodents. Taken together, these results suggest that the mixed herbal formula DA-9805 may be a pharmaceutical agent for preventing or improving PD.