Objective: Tricellulin plays a central role in the sealing of epithelia at tricellular contacts. We examined the effects of Snail, an epithelial-mesenchymal transition (EMT)-related transcription factor, on the regulation of tricellulin expression in human gastric carcinoma (GC)-derived cells. Method: Six human GC-derived cell lines were used in this study. Expression and localization of tricellulin was analyzed by reverse transcription (RT)-PCR and immunohistochemistry. Also, a Snail expression vector was transfected into HSC-45 cells to examine altered mRNA levels of tricellulin, E-cadherin, vimentin, N-cadherin and several EMT transcription factors by quantitative real-time RT-PCR. Results: Abundant tricellulin expression was detected in all GC-derived cells examined. In HSC-45 cells, transduction of Snail decreased the expression levels of tricellulin and E-cadherin but increased vimentin and N-cadherin, which was accompanied by induction of EMT transcription factors such as Twist1, Twist2 and Slug. In normal gastric mucosa, tricellulin protein was localized at the tricellular tight junction; however, in HSC-45 cells, tricellulin protein was distributed in the cytoplasm. In GC tissues, tricellulin expression at the cellular membrane was retained in a subset of EMT-negative GCs, and it disappeared in EMT-positive GCs. Conclusions: The findings in the present study suggest that repression of tricellulin expression may be related to Snail-induced EMT in human GCs.