Abstract: Cisplatin (Cis) is a potent chemotherapeutic agent; however, it is linked with oxidative stress, inflammation, and apoptosis, which may harmfully affect the brain. Hypericum perforatum L. (HP L.) is a strong medicinal plant, but its hydrophobic polyphenolic compounds limit its activity. Therefore, our study aimed to investigate the neuroprotective action of HP L. and its nanoemulsion (NE) against Cis-induced neurotoxicity. The prepared HP.NE was subjected to characterization. The droplet size distribution, surface charge, and morphology were evaluated. In addition, an in vitro dissolution study was conducted. Compared to Cis-intoxicated rats, HP L. and HP.NE-treated rats displayed improved motor activity and spatial working memory. They also showed an increase in their antioxidant defense system and a reduction in the levels of pro-inflammatory cytokines in the brain. Moreover, they showed an increase in the expression levels of the PON-3 and GPX genes, which are associated with a reduction in the brain levels of COX-2 and TP-53. These findings were confirmed by reducing the immunohistochemical expression of nuclear factor kappa (NF-ƘB) and enhanced Ki-67 levels. In conclusion, HP L. is a promising herb and could be used as an adjuvant candidate to ameliorate chemotherapeutic-induced neurotoxicity. Moreover, HP.NE has superior activity in lessening Cis-induced oxidative stress, inflammation, and apoptosis in brain tissue.