1. Climate-associated changes in forest composition have been widely reported, particularly where changes in abiotic conditions have resulted in high mortality of sensitive species and have disproportionately favored certain species better adapted to these newer conditions. In the northeastern USA and southeastern Canada, few studies have examined climate-related influences associated on forest composition, and none have considered broad-scale changes over a long temporal (>25 years) period. 2. We used US Forest Service Forest Inventory and Analysis data from 1983-2014 across four northeastern states (Maine, New Hampshire, New York, and Vermont) to assess temporal and spatial changes in the occurrence and abundance of American beech, sugar maple (Acer sacharum L.), red maple (A. rubrum L.), and birch (Betula spp.) saplings. We also tested the effects of biotic and abiotic factors on the distribution of the four studied deciduous species over the entire studied period. 3. Occurrence and abundance of American beech have increased substantially over the past three decades, whereas the occurrence and abundance of three-other deciduous species have decreased in all ecological provinces of the northeastern USA, except the Midwest Broadleaf ecological province. Consequently, a clear shift in species composition is currently underway in the beech-maple-birch (BMB) forests of the northeastern USA, with uncertain consequences for future ecosystem structure and function. 4. In the studied region and over the entire studied period, the distribution of increased occurrence and abundance of beech relative to three-other deciduous species were associated with the higher temperature and precipitation as well as higher conspecific basal area and dead tree basal area. 5. Synthesis and applications: The change from BMB forests to beech-dominated forests and beech encroachment to new forest areas across the northeast may expand in areas where higher intensity harvesting/disturbances (i.e., large-scale canopy openings) do not occur, which would be a management concern as the beech is associated with the beech-bark disease. Our results emphasize the need for management strategies such as higher intensity harvesting methods, vegetation management, and controlling browsing pressure to reduce the beech dominance.