The aim of this study was to determine the activity concentrations and radiological hazard parameters of Cs-137 and K-40 in soft tissue samples of sea snails (Rapana venosa) collected from 12 different stations in the East Black Sea coastal area of Turkey. The values in soft tissues of sea snail samples with three different sizes were between 0.31 and 1.79 Bq kg(-1) for Cs-137 and 163.9 and 269.4 Bq kg(-1) for K-40. The mean activity concentrations of Cs-137 and K-40 in tissues of small-sized sea snails were determined to be higher than those of Cs-137 and K-40 in soft tissues of the other sizes. The determined activity concentration values were lower than the concentrations reported in similar studies. Radiological hazard parameters such as the daily intake (Dint) of Cs-137 and K-40, annual committed effective dose (E-eff), and lifetime cancer risk (LCR) were calculated and compared with the international recommended values.