Background <p>Given that there is not yet a fully effective treatment for Parkinson’s disease (PD), further research into therapeutic agents is necessary to enhance PD patients’ clinical performance and quality of life. Stigmasterol (ST) exerts some pharmacological effects on the nervous system, such as antioxidant, anti-apoptosis, anti-inflammation, and modulation of autophagy, but its potential effects on PD are unclear. This study aimed to determine whether ST exerted neuroprotective benefits in a PD model and to clarify the underlying molecular mechanism.</p> Methods <p>We performed behavioral, immunohistochemical, immunofluorescence, western blot, and biochemical index assays in 1-methyl-4-phenylpyridinium (MPP⁺)-induced PD cell model and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse model to evaluate the impacts of ST on dyskinesia, the degree of dopaminergic neuron degeneration, and the prooxidant–antioxidant system, as well as the signaling pathways underlying its neuroprotective actions.</p> Results <p>We found that ST in the PD model activated the Kelch-like ECH-associated protein 1 (Keap1)/nuclear factor-erythroid 2-related factor 2 (Nrf2) signaling pathway and promoted the Nrf2 nuclear translocation. Additionally, it increased the antioxidant enzymes expression, thereby attenuating reactive oxygen species (ROS)-induced oxidative stress, which in turn, slowed the dopaminergic neuron loss by inhibiting apoptotic pathways, and improved the tyrosine hydroxylase (TH) protein expression, and helped reduce motor impairments in the PD mouse model.</p> Conclusions <p>Our results indicate that ST has an antioxidant role in the PD model through activating the Keap1/Nrf2 signaling pathway, offering a theoretical foundation for its potential therapeutic use in PD treatment.</p>