Concentrations of trace metals, cadmium (Cd), zinc (Zn), copper (Cu), lead (Pb), chromium (Cr), and nickel (Ni) were determined in Magnificent Frigatebird (Fregata magnificens) harvested in Sepetiba Bay, Rio de Janeiro, Brazil. Mean concentration levels in liver and kidney (µg.g-1 dry weight) were 8.04 and 5.57 (Cd); 66.44 and 54.64 (Zn); 45.29 and 46.89 (Cu); 44.67 and 37.35 (Pb); 2.94 and 5.02 (Cr); and 8.12 and 5.98 (Ni), respectively. Nowadays, there is growing conviction that seabird surveys provide important geographical and temporal evidence patterns of aquatic ecosystems conditions, and for this reason the present study provides new insights to use seabirds as bio-sentinel for aquatic pollutants. The results reflect higher concentrations of metals in F. magnificens. These findings are highly the importance of heavy metals accumulation in the aquatic system and portend a serious health risk to human consumption and along marine trophic chains.