The isotopic composition of species-specific atmospheric mercury (Hg) was investigated in the coastal environment of Grand Bay, Mississippi, USA. Atmospheric mercury species (Hg⁰_(g), Hg^II_(g) and Hg_(p)) were collected individually, and analyzed for isotopic composition. Gaseous elemental Hg (Hg⁰_(g)) displayed δ²⁰²Hg ranging from −3.88‰ to −0.33‰. Aerosol Hg (Hg_(p)) displayed intermediate δ²⁰²Hg ranging from −1.61‰ to −0.12‰, while reactive gaseous Hg (Hg^II_(g)) displayed positive δ²⁰²Hg ranging from +0.51‰ to +1.61‰. Significant positive mass-independent fractionation (MIF) was observed in Hg_(p) (∆¹⁹⁹Hg=+0.36‰ to +1.36‰), while Hg⁰_(g) displayed negative MIF (∆¹⁹⁹Hg=−0.41‰ to −0.03‰) and Hg^II_(g) displayed intermediate MIF (∆¹⁹⁹Hg=−0.28‰ to 0.18‰). Positive MIF of ¹⁹⁹Hg and ²⁰¹Hg measured in Hg_(p) is consistent with significant in-aerosol photoreduction. Significant MIF of ²⁰⁰Hg was observed in all Hg species with Hg⁰_(g) displaying negative ∆²⁰⁰Hg values of −0.19‰ to −0.06‰ while Hg^II_(g) and Hg_(p) displayed positive ∆²⁰⁰Hg values of +0.06‰ to +0.28‰, which are similar to ∆²⁰⁰Hg values reported by Gratz et al. (2010). These results suggest that isotope tracing of each atmospheric Hg species may be feasible during important atmospheric processes such as wet and dry deposition.