BACKGROUND: Recent studies highlight the crucial role of endothelial cell-specific molecule 1 (ESM1) in the development of multiple cancer types. However, its aberrant expression and prognostic value in human pan-cancer have largely not been described. METHODS AND RESULTS: In this study, we used The Cancer Genome Atlas (TCGA) analysis databases to explore the expression level and prognostic significance of ESM1 in 33 types of human cancer. ESM1 was shown to be over-expressed in 12 cancer types, including BLCA, BRCA, COAD, CHOL, ESCA, HNSC, KIRC, KICH, LIHC, STAD, THCA, and UCEC. The expression of ESM1 was significantly correlated with the overall survival (OS) of patients in CESC, ESCA, KIRC, and KIRP. In addition, high ESM1 level indicated poor disease-free survival (DFS) of patients with ACC, ESCA, PRAD, LIHC, KIRP, and UCS. Through comparative analysis, we discovered that ESM1 was dramatically up-regulated in esophageal cancer (ESCA) and associated with worse patient OS and DFS. The elevation of ESM1 in ESCA was confirmed by the datasets from Cancer RNA-Seq Nexus (CRN) and Gene Expression Omnibus (GEO). Based on Gene Set Enrichment Analysis (GSEA), we analyzed the co-expressed genes of ESM1 in ESCA, and found that ESM1 was closely implicated in cell proliferation and migration and the regulation of Janus kinase (JAK) signaling pathway. Functionally, knockdown of ESM1 significantly suppressed cell proliferation and migration, and decreased the protein level of JAK1. CONCLUSIONS: Taken together, our results suggest for the first time that ESM1 functions as an oncogene and may be a clinical biomarker and/or therapeutic target in ESCA.