Studies that assess mercury bioaccumulation in small carnivores in terrestrial habitats are limited. We quantified total mercury (THg) in American marten (Martes americana) that were harvested for fur in Michigan, US, during 2013 and 2014. We quantified THg (dry weight) in hair, kidney, and liver samples and further analyzed hair for potential demographic and ecological factors that influence THg bioaccumulation. We found THg concentrations to be the highest in hair (1.228±0.475 µg/g, n=40), followed by kidney (0.922±0.651 µg/g, n=29) and liver (0.344±0.219 µg/g, n=26). Total mercury distributed predictably and significantly between tissue types, and hair was moderately predictive at modeling THg in kidney (R²=0.50, P<0.001, n=29) and weakly predictive in liver (R²=0.35, P<0.001, n=26), suggesting that hair, which is easily obtained, could be a useful sample type for future biomonitoring programs. The concentrations of THg in hair were higher in adults relative to juveniles, and adult female martens had the highest levels of THg (1.980±0.188 µg/g), as compared to juveniles and adult males. Results of generalized linear modeling suggested that THg hair concentrations were positively associated with marten age and trophic position (stable isotope ratio, δ¹⁵N). An interaction between δ¹⁵N and the year marten carcasses were collected showed that δ¹⁵N alone could be highly predictive of THg in some years but not in others. Annual changes in diet could lead to differing rates of mercury bioaccumulation and alter the usefulness of δ¹⁵N to predict THg in marten tissues. Further research should explore the connections between changes in prey availability, types of prey consumed, and the influence on bioaccumulation rates of mercury in terrestrial system mesocarnivores.