The k
0-standardized neutron activation analysis (k
0-NAA) has been applied for determination of multiple elements (25 elements: Al, As, Ba, Br, Ca, Cl, Co, Cr, Cs, Cu, Eu, Fe, Hg, K, La, Mg, Na, Rb, Sc, Se, Sm, Th, Ti, V and Zn) in marine sediment and tuna fish. About 50 marine sediment and 9 tuna fish samples were collected in two coastal areas of Vietnam. The health risk index (HRI) values of As and Br were higher than 1.0 for the tuna fish. Also, HRI value of Hg was 8.92 × 10−1 indicating a relatively high potential health risk, whiles Co and Mn with HRIs = 1.56 × 10−4 and 8.56 × 10−4, respectively, have the lowest potential health risks. Average enrichment factors using Al as a reference element (EF
Al) were higher than 1.5 for Eu, La, Zn, Th, Cs and As in which the highest EF
Al value for As was higher than 10. This study showed that the HRI value of As in the tuna fish correlated positively with the EF
Al value for the element in the marine sediment.