The concentrations of some heavy metals (Cu, Zn, Pb and Cd) were investigated in the sediments and in the mullet Liza klunzingeri from the northern part of the Persian Gulf. The levels of Cu, Zn and Pb in the sediment varied significantly among the sampling sites (P < 0.05). Sediments from the northern part of the Persian Gulf had serious ecological risk when considering PER. The ranges of the average concentrations of Cu, Zn, Pb, and Cd in the tissue of L. klunzingeri were 10.00–16.66 mg/kg, 18.75–32.50 mg/kg, 3.25–14.16 mg/kg and 0.37–3.33 mg/kg, respectively. The health risk analysis of individual heavy metals in the fish tissue indicated dangerous levels of Pb and Cd for the general population at some sampling sites.