Invasive plants may disrupt symbioses between plants and soil biota. We tested whether ectomycorrhizal fungi (ECM) associating with Quercus rubra (Northern Red Oak) seedlings was lower near invasive Alliaria petiolata (Garlic Mustard). We quantified ECM colonization, identified morphotypes, and compared composition in forests with contrasting Garlic Mustard densities. Seedlings had lower ECM colonization and diversity in a stand with dense Garlic Mustard than in a stand without Garlic Mustard. ECM composition also differed between stands. Seedlings in a stand with moderate density Garlic Mustard had marginally less ECM than those at the no Garlic Mustard site. These findings suggest that ECM association is negatively correlated with Garlic Mustard invasion. This association may result in lasting changes to forest communities and hinder site restoration following Garlic Mustard removal.