To investigate the role of the translocase of the outer mitochondrial membrane 40 (TOM40) in oral squamous cell carcinoma (OSCC) with the aim of identifying new biomarkers or potential therapeutic targets.TOM40 expression level in OSCC was evaluated using datasets downloaded from The Cancer Genome Atlas (TCGA), as well as clinical data. The correlation between TOM40 expression level and the clinicopathological parameters and survival were analyzed in TCGA. The signaling pathways associated with TOM40 were identified through gene set enrichment analysis. A network of genes co-expressed with TOM40 was constructed and functionally annotated by gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. The immune infiltration pattern in OSCC was analyzed in the TCGA-OSCC cohort using the CIBERSORT algorithm. Clinically significant factors of OSCC were screened through the expression levels of TOM40 and a clinically relevant nomogram was constructed. The TCGA-OSCC cohort was divided into the TOM40high and TOM40low groups and the correlation between TOM40 expression level and the sensitivity to frequently used chemotherapeutic drugs was evaluated. CCK-8 and colony formation assays were applied to determine the cell growth.TOM40 was highly expressed in OSCC tissues and correlated negatively with the overall survival (P < 0.05). Patients with high TOM40 expression level showed worse prognosis. Furthermore, GO and KEGG enrichment analyses of the differentially expressed genes related to TOM40 showed that these genes are mainly associated with immunity and tumorigenesis. Immunological infiltration analysis has found that the expression levels of TOM40 are correlated with the proportions of several immune cells. Moreover, we found that TOM40 knockdown inhibited cell growth in OSCC cell lines.Our results uncovered that TOM40 is a reliable prognostic marker and therapeutic target in OSCC.© 2024. The Author(s).