The purpose of this study was to quantify the level of mercury found in the newly invasive oysters (Crassostrea gigas) from the San Diego Bay and to perform a human health risk assessment for those who harvest these recreationally or for subsistence. Individual oysters from San Diego Bay were sampled at 11 sites throughout the Bay and analyzed for total Hg using the DMA-80, Milestone Direct Mercury Analyzer. The results showed oyster tissue total Hg levels ranged from 0.0136 mg/kg in wet weight (ww) to 0.0476 mg/kg (ww) with a mean value of 0.0285 mg/kg (ww). Using a ratio value of methyl mercury (MeHg): total Hg in oyster tissues sampled of 0.37, a risk assessment was conducted. In this risk assessment, there were four scenarios of mercury exposure and risk to human health that were evaluated. These included two scenarios, one using the mean total Hg (converted to MeHg) concentration measured in this study, and the other using the maximum value observed. Additionally, two rates of oyster consumption were evaluated in two exposure scenarios, a subsistence population consuming 0.1424 kg/day and an average consuming population (0.009 kg/day). The result of the risk assessment indicated that no adverse health effects are likely to occur for both subsistence consumers and non-subsistence consumers who may harvest and eat the newly invasive oyster (Crassostrea gigas) from San Diego Bay. Our study also found no significant associations between the size and weight of oysters and the total Hg levels, and that levels of total Hg were quite uniform among the 11 sites sampled (except for the single G street site). This later finding reflects a diffuse atmospheric source of mercury rather and the ubiquitous nature of mercury contamination in San Diego Bay.