<p>Prenatal exposure to valproic acid (VPA), a widely prescribed antiepileptic and mood‑stabilizing drug, is a well-established environmental risk factor for autism spectrum disorder (ASD). Although behavioral and anatomical abnormalities have been reported in VPA-exposed animal models, the underlying molecular mechanisms within specific brain regions remain unclear. In this study, we used tandem mass tag (TMT)-based quantitative proteomics to profile protein expression in the striatum of 9–10-week-old mice prenatally exposed to VPA. Behavioral assessment confirmed core ASD-like phenotypes, including reduced body and brain weights and increased repetitive self-grooming behavior. Proteomic profiling identified 101 differentially expressed proteins (DEPs), with 47 upregulated and 54 downregulated in VPA-exposed mice. Functional enrichment analysis revealed significant involvement of pathways related to synaptic transmission, neuronal development, metal ion homeostasis, oxidative stress response, and excitation/inhibition (E/I) balance. Notably, proteins such as parvalbumin (PVALB), NR2F1, and metallothioneins (MT1, MT2, MT3) were markedly downregulated, implicating impaired inhibitory signaling and redox regulation. Importantly, quantitative PVALB immunofluorescence analysis provided histological validation of the proteomic findings, revealing a significant reduction of PVALB immunoreactivity in the dorsolateral striatum, with a non-significant trend toward reduction in the dorsomedial striatum. Additionally, protein–protein interaction network analysis identified PVALB and MT2 as central hub proteins linking synaptic, glial, and oxidative stress-related modules, highlighting disrupted striatal network organization. Collectively, these findings provide subregion-specific molecular and histological insight into how prenatal VPA exposure alters striatal neurobiology and contributes to ASD-like behavioral phenotypes. Proteomic data are available via ProteomeXchange (PXD067574).</p>