We investigated the distribution of trace metals (spatial and temporal) and sedimentary particles in order to identify the relationship between benthic foraminifera and trace metals pollution within Gunnamatta Bay, Port Hacking Estuary, NSW, Australia. Risk assessments of surface sediments were evaluated by using hierarchical cluster analysis (HCA). A total of 59 surface sediment samples and seven subsurface sediment samples were collected, in order to determine the levels of trace metals in spatial and temporal of the bay. Further, six surface sediment samples were examined for existing foraminiferal assemblages in muddy samples, which had high and low concentration of trace metals and sandy samples. The trace metals distribution showed that the trace metals such as chromium, nickel, copper, zinc, arsenic, lead, rubidium and bromine had similar distribution in surface sediments. The results of trace metal concentrations were compared with the deleterious biological effect values in marine sediments. The mean of most trace metals for the Bay were below the Effect Range Low except copper and Effect Range Median. The highest concentrations of these metals were found to be in the north east of the bay sample GU55, which is close to the proximity of discharge points, and craft boats (moored) with concentrations (107, 14, 398, 413, 8, 203, 27 and 182ppm) respectively. Also, this trace metal pollution is concentrated in the inner part of the bay, which is deep, and has organic matter and clay minerals. The benthic foraminferal assemblages has low species diversity in muddy samples GU25 and GU55 compared to the fine sandy particles in samples GU12 and GU24. Furthermore, the muddy particles that have had high level of trace metals were dominated by species tolerant- pollution such as Ammonia beccarii, Brizalina spathulata and Elphidium excavatum. These have had more opportunity to flourish. In addition, the values of trace metals dramatically decline with increasing depth. This reflects that the potential source of trace metal pollution is from human activity (eg. gasoline fumes and boats), since early European settlement in this area.