Dysregulation of the microbiota–gut–brain axis has been implicated in Parkinson’s disease (PD), and modulation of the intestinal microbiota may offer a complementary nutritional approach. This study evaluated the preventive attenuation of MPTP-induced PD-like abnormalities by Lactiplantibacillus plantarum SHOU LAC-1 and examined associated microbiota–gut–brain axis-related changes. Forty male C57BL/6J mice were allocated to Control, MPTP, L-DOPA, and SHOU LAC-1 groups (n = 10 per group). SHOU LAC-1 was orally administered at 1 × 109 CFU per mouse per day for 42 days, with MPTP administered during the final 14 days; L-DOPA was administered during the MPTP-treatment period as a positive control. Motor performance and defecatory parameters, nigrostriatal TH and α-SYN immunoreactivity, neurotrophic-support-related gene expression, inflammatory markers, glial-cell-related gene expression, Nrf2-related antioxidant gene expression, colonic histopathology and tight-junction-related gene expression, gut microbiota composition, and serum metabolic profiles were assessed. Compared with MPTP-treated mice, SHOU LAC-1-treated mice showed better motor and defecatory performance, partial preservation of nigrostriatal TH immunoreactivity, reduced α-SYN immunoreactivity, increased neurotrophic-support-related gene expression, lower central and colonic inflammatory markers and glial-cell-related gene expression, increased Nrf2/HO-1/NQO1-related antioxidant gene expression, and comparatively better-preserved colonic morphology with higher tight-junction-related gene expression. 16S rRNA sequencing and untargeted serum metabolomics further showed that SHOU LAC-1 administration was accompanied by changes in gut microbial diversity and composition and serum metabolic profiles. Overall, under this preventive experimental design, SHOU LAC-1 administration was associated with attenuation of multiple MPTP-induced PD-like abnormalities, accompanied by changes in gut microbial and serum metabolic profiles. These preclinical findings are predominantly associative; causal relationships among microbial, metabolic, intestinal, and neurological changes remain to be established, and the translational relevance of SHOU LAC-1 requires further validation.