Earthworms introduced to formally glaciated parts of North America have the potential to adversely affect forested habitats across the region. In order to investigate potential impacts of earthworms on plant diversity in a New England forest, we documented the biomass of invasive earthworms and tallied plant diversity at Ice Glen preserve in the western Massachusetts town of Stockbridge. Given the profound role of earthworms as ecosystem engineers, we investigated whether mean invasive earthworm biomass was correlated with plant species diversity (richness and phylogenetic diversity). We found that a high biomass of invasive earthworms coincided with reduced total plant phylogenetic diversity and species richness, in addition to reduced richness of native plants, and increased abundance of non-native plants. This study provides insight into the potential impacts of introduced earthworms on forest plants in New England.