To utilize a saline coastal mud flat, seawater-cultivated vegetables were bred and planted in Jiangsu Province, P. R. China. Due to ubiquitous heavy metal pollution in coastal areas and high bioaccumulation potential of heavy metals in halophytes, food safety of seawater-cultivated vegetables should be a public concern. In the present study we collected three seawater-cultivated vegetable species (Suaeda glauca, Salicornia europaea and Portulaca oleracea), soils, seawater and freshwater runoff from five locations in Jiangsu Province. Concentrations of Cu, Zn, Cr, Cd, Pb and Ni in these samples were determined. The results showed that all soil samples showed a low level of heavy metals and complied with the Chinese Environmental Quality Standard for Soils, but seawater and freshwater runoff surrounding sampling sites displayed a high level of Cu an Pb, suggesting a high risk of heavy metal contamination. Levels of Cr and Pb in all investigated plant species were sometimes higher than the limits in the Chinese Standard of Food Safety, suggesting potential risk to food safety. Overall, seawater-cultivated vegetables might accumulate heavy metals and subsequently endanger the health of human beings when planting on saline soils.