Background <p>As the relationship between oral microbiota and treatment efficacy in esophageal cancer remains unexplored, we aimed to clarify it using metagenomic analysis.</p> Patients and Methods <p>Of the 140 consecutive patients with esophageal squamous cell carcinoma (ESCC) who underwent esophagectomy with R0 resection at Hiroshima University Hospital between April 2020 and May 2024, 74 who received neoadjuvant therapy were included in this study. 16S rRNA gene from oral tongue coating samples was amplified using polymerase chain reaction and subjected to next-generation sequencing. The oral microbiome data were analyzed using QIIME2 and linear discriminant analysis effect size, and the relationship between the oral microbiota and treatment efficacy and prognosis was assessed.</p> Results <p>Alpha diversity of the oral microbiota was significantly correlated with the pathological response. Univariate and multivariate analyses showed that the alpha diversity of the oral microbiome (high versus low) was a significant predictor of a good pathological response. Patients with high alpha diversity had significantly improved recurrence-free survival and overall survival compared with those with low alpha diversity. Furthermore, eight bacterial groups (<i>Lactobacillales</i>, <i>Peptostreptococcales-Tissierellales</i>, <i>Bifidobacteriaceae</i>, <i>Erysipelotrichaceae</i>, <i>Lactobacillaceae</i>, <i>Anaerovoracaceae</i>, <i>Staphylococcaceae</i>, and <i>Aerococcaceae</i>) were significantly more abundant in individuals who responded well to neoadjuvant therapy and two bacterial groups (<i>Streptococcaceae</i> and <i>Corynebacteriaceae</i>) were significantly more abundant in poor responders.</p> Conclusions <p>Our results demonstrate a correlation between the oral microbiome and ESCC treatment efficacy, suggesting that it is a significant prognostic factor. Our findings may also help predict the efficacy of esophageal cancer treatment.</p>