In northeastern temperate forests, eastern hemlock (Tsuga canadensis) has been experiencing defoliation and subsequent mortality from infestations of hemlock woolly adelgid (HWA; Adelges tsugae), an invasive exotic aphid-like insect. Eastern hemlock hosts a range of ectomycorrhizal (EM)-fungal symbionts. Changes in forest health and composition that follow eastern hemlock decline may co-occur with changes in EM fungal species and altered soil conditions. This study examines the effects of HWA-induced defoliation on EM communities and soil abiotic variables in a watershed of a mixed conifer-hardwood forest in southeastern New York. EM communities were compared among HWA-infested and healthy eastern hemlock-dominated stands and oak (Quercus spp.) dominated stands. Soil cores were collected in June, August and October of 2004 and ectomycorrhizal species on root tips were identified by morphotype. Soil extractable nitrogen (N), soil moisture, and pH were measured in soils and analyzed with respect to forest type. In August and October, the oak-dominated stands had greater morphotype richness than the HWA-infested hemlock-dominated stands. In June and October, the HWA-infested hemlock-dominated stands had higher levels of NO3- than the healthy hemlock-dominated stands. pH was higher in the oak-dominated stands than the HWA-infested hemlock-dominated stands in August and October. HWA-infested hemlock-dominated stands had higher gravimetric water content than oak-dominated stands in October. Results show that HWA-induced defoliation results in lower EM morphotype richness, higher nitrate concentrations, lower pH and higher soil moisture.