This study was conducted to determine the concentration of five heavy metals, including lead, cadmium, mercury, arsenic, and chromium in muscle, liver and gills of the gray mullet, Liza aurata in southern part of the Caspian Sea. The samples were collected during sexual maturity (in the fall) and sexual rest (in the spring). The mean concentration of lead, cadmium, mercury, arsenic, and chromium in the muscle tissue were 1.40, 0.43, 0.16, 0.07 and 0.54 µg/g, respectively during sexual maturity and 1.90, 0.93, 0.24, 0.12 and 0.61 µg/g, respectively during sexual rest. Generally, the uptake of heavy metals during sexual rest was higher (Pb>Cd>Cr>Hg>As) than that (Pb>Cr>Cd>Hg>As) during sexual maturity. Pollutants are effective in the accumulation of heavy and toxic metals in L. aurata in the Caspian Sea during different seasons. The concentration pattern of the metals in the three tissues was as follows: liver>gill>muscle. The difference between the concentrations of the metals in studied tissues was significant. A highly significant correlation between the elements in tissues was observed in both sexual periods. The comparison of the data obtained for muscle tissue with the WHO and NHMRC guidelines showed that the concentrations of all the five heavy metals (Pb, Cr, Cd, Hg, As) were higher than the global standard levels for these metals.