This study presents concentrations of heavy metals in tissues of Black-crowned night herons (Nycticorax nycticorax), age-related variations related to the growth stage from chicks to adults, and comparison of concentrations between chicks and adults. Heavy metal differences by growth stage from chicks to adults were observed for iron concentrations in the muscle; manganese concentrations in the kidney; zinc and copper concentrations in the muscle; lead concentrations in the liver, kidney, and bone; and cadmium concentrations in the kidney. Comparing chicks with adults, iron concentrations in the kidney and bone of adults were higher than those of chicks. Copper concentrations in the muscle of adults were higher than those of chicks. Lead concentrations in the liver and bone were lower in adults than in chicks. Manganese, zinc and cadmium concentration of each tissue did not significantly differ between adults and chicks. We suggest that concentrations of iron, manganese, zinc and copper varied with the metabolic turnover for growth of chicks. In this study, lead concentrations of adults and cadmium concentrations of chicks and adults were within the range of background levels for wild birds, only lead concentrations of chicks were within the range of a level consistent with elevated lead exposure.