Forest ecosystems will be affected directly and indirectly by a changing climate over the 21st century. This assessment evaluates the vulnerability of 11 forest ecosystems in the Mid-Atlantic region (Pennsylvania, New Jersey, Delaware, eastern Maryland, and southern New York) under a range of future climates. We synthesized and summarized information on the contemporary landscape, provided information on past climate trends, and described a range of projected future climates. This information was used to parameterize and run multiple forest impact models, which provided a range of potential tree responses to climate. Finally, we brought these results before two multidisciplinary panels of scientists and land managers familiar with the forests of this region to assess ecosystem vulnerability through a formal consensus-based expert elicitation process. Analysis of climate records indicates that average temperatures and total precipitation in the region have increased. Downscaled climate models project potential increases in temperature in every season, but vary in projections for precipitation. The forest impact models project declines in growth and suitable habitat for many mesic species, including American beech, eastern hemlock, eastern white pine, red spruce, and sugar maple. Species that tolerate hotter, drier conditions are projected to persist or increase, including black oak, northern red oak, pignut hickory, sweetgum, and white oak. The montane spruce-fir and lowland conifer forest communities were determined to be the most vulnerable ecosystems in the interior portion of the Mid-Atlantic region. Maritime and tidal swamp forest communities were determined to be the most vulnerable ecosystems in the coastal plain portion of the region. The woodland, glade, and barrens forest community was perceived as less vulnerable to projected changes in climate. These projected changes in climate and the associated impacts and vulnerabilities will have important implications for economically valuable timber species, forest-dependent animals and plants, recreation, and long-term natural resource planning.