Heavy metal concentrations in some macrobenthic fauna have been reported for the first time from the Sundarbans mangrove forest, south west coast of Bangladesh, in the northern part of Bay of Bengal. The concentration of Fe, Cu, Zn, Cd and Pb in macrobenthos ranged from 235 ± 10.11 to 1,051 ± 38.42, 3.66 ± 0.89 to 7.55 ± 1.29, 76.8 ± 8.55 to 98.5 ± 6.49, 0.46 ± 0.11 to 0.859 ± 0.2 and 4.66 ± 1.17 to 6.77 ± 2.1 μg/g, respectively. Significant variations (p ≤ 0.05) in heavy metal concentrations have been observed among the mud crab, mudskipper and gastropod. However, heavy metal burdens did not vary significantly among the hermit and horseshoe crabs. In mud crab, horseshoe crab and gastropod, heavy metal concentrations were recorded in the sequence: Fe > Zn > Pb > Cu > Cd. Hermit crab and mudskipper contained heavy metals in the order of Fe > Zn > Cu > Pb > Cd. Fe and Zn concentrations were found significantly (p ≤ 0.05) higher in macrobenthos. The lead (Pb) concentration found in the edible portion of macrobenthos exceeded the international permissible limits certified by the WHO. Bioconcentration factors >1.00 obtained for Fe (17.05 in mudskipper) and Cd (1.87 in gastropod) indicated that these metals were highly bioaccumulated and biomagnified in benthic fauna of Sundarbans. The findings of this study refer to the potential impact of heavy metals in the mangrove ecosystem of Bangladesh.