The study of the gut microbiota's impact on brain functions has revealed a significant correlation, with the dysregulation of the gut–brain axis being linked to neurological disorders. The gut microbiota and brain communicate via four main routes, with the vagus nerve being the most crucial mode connecting the GI tract to the brain stem. Recent studies reveal that enteric pathogens and probiotics can influence host behaviors like anxiety, feeding, and depression by altering GABA, oxytocin, and BDNF signaling in the brain. Certain gut bacteria metabolites are linked to an increase in reactive oxygen species levels, a significant risk factor for neurodegeneration. Gut bacteria metabolites not only contribute to the development of life-threatening brain disorders but also play a crucial role in their prevention. Recent studies highlight two crucial connections between the gut microbiota and the brain: "gut microbiota–oxidative stress–neurodegeneration" and "gut microbiota–antioxidant–neuroprotection." This review provides a comprehensive overview of studies examining gut microbiota-mediated oxidative stress in neurodegeneration and the microbiota's role in neuroprotection. Traumatic Brain Injury (TBI), a prevalent injury with an annual incidence of around 1.4 million in the US, is a major cause of death and disability worldwide. TBI disabilities involve primary brain damage, secondary cellular and molecular damage, and metabolic anomalies, leading to temporary or lifelong cognitive impairments. TBI, a heterogeneous pathobiological condition, presents with multiorgan damage and lacks therapies due to its heterogeneous nature, necessitating the consideration of novel therapeutic regimens. Gut eubiotic therapeutics have gained significant attention due to their ability to restore the bifacial relationship between gut dysbiosis and type 2 diabetes. The detection of gut microbiota modulation could serve as a diagnostic tool for identifying TBI severity, thereby enabling the development of targeted therapeutic approaches.