Tetrodotoxin (TTX) is a potent neurotoxin commonly found in pufferfish and various marine invertebrates. Previous studies conducted in southern Taiwan and Japan have reported that species within the genus Umbonium, a group of marine trochid snails, act as vectors for TTX. Although these trochid snails are also commonly found on sandy or muddy tidal flats along the west and south coasts of Korea, no studies have yet investigated the presence of TTX in these snails. In this study, we screened U. costatum, a species widely distributed along Korea's west and south coasts, for the presence of TTX. In 2023, we collected U. costatum specimens from Myeongsa Beach on the south coast and Seonyudo Beach on the west coast, and analyzed their tissues for TTX using a competitive enzyme-linked immunosorbent assay (cELISA). The cELISA results indicated that TTX concentrations in the tissues of all collected snails were below the detection limit. Based on these findings, it appears that U. costatum from the west and south coasts of Korea may lack the capacity to accumulate TTX, or the absence of TTX may be due to the lack of TTX-containing prey in their environment. However, further investigations, including monthly toxicity screenings and studies on the TTX tolerance capacity of U. costatum, are needed to understand TTX dynamics in this species better.