AbstractThe ketogenic diet (KD) is a low‐carbohydrate, high‐fat regime that is protective against neurodegenerative diseases. However, the impact of KD on Parkinson's disease (PD) and its mechanisms remains unclear. 1‐Methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP)‐induced mouse model of PD was fed with KD for 8 weeks. Motor function and dopaminergic neurons were evaluated. Inflammation in the brain, plasma, and colon tissue were also measured. Fecal samples were assessed by 16S rDNA gene sequencing and untargeted metabolomics. We found that KD protected motor dysfunction, dopaminergic neuron loss, and inflammation in an MPTP mouse model of PD. 16S rDNA sequencing revealed that MPTP administration significantly increasedCitrobacter,Desulfovibrio, andRuminococcus, and decreasedDubosiella, whereas KD treatment reversed the dysbiosis. Meanwhile, KD regulated the MPTP‐induced histamine, N‐acetylputrescine,d‐aspartic acid, and other metabolites. Fecal microbiota transplantation using feces from the KD‐treated mice attenuated the motor function impairment and dopaminergic neuron loss in antibiotic‐pretreated PD mice. Our current study demonstrates that KD played a neuroprotective role in the MPTP mouse model of PD through the diet–gut microbiota–brain axis, which may involve inflammation in the brain and colon. However, future research is warranted to explore the explicit anti‐inflammatory mechanisms of the gut–brain axis in PD models fed with KD.