ERBB2 is a member of the epidermal growth factor receptor (EGFR) family. Recent studies revealed that the kinase domain of the ERBB2 gene was mutated in human cancers, including gastric cancer. Despite the importance of cancer metastasis in the pathogenesis of cancers, data on the ERBB2 kinase domain mutation in cancer metastasis are lacking. In this study, to explore the possibility that ERBB2 mutation is involved in the metastasis mechanism, we analyzed the kinase domain of ERBB2 for the detection of somatic mutations in 58 gastric adenocarcinomas with lymph node metastasis. We found one ERBB2 mutation, which was detected in the lymph node metastasis, but not in the primary tumor of the same patient. The ERBB2 mutation was a missense mutation which substituted an amino acid in exon 21 (V832I). We simultaneously analyzed the somatic mutations of EGFR, K-RAS, PIK3CA and BRAF genes in the sample with the ERBB2 mutation, and found that this metastatic carcinoma did not harbor any of the mutations. Our data suggest that ERBB2 kinase domain mutation occasionally occurs in metastatic gastric carcinoma and might play a role in the metastatic process of some gastric carcinomas.