The northeast side of Glastenbury Mountain drains into Deer Lick Brook, thence into the Glastenbury River, the Deerfield River, the Connecticut River, and into Long Island Sound in Connecticut. The southeast side of Glastenbury Mtn. drains into Deer Cabin Brook, and thence into the Glastenbury River. The southwest end of Glastenbury Mtn. drains into Bolles Brook, thence into the Roaring Branch of the Walloomsac River, the Hoosic River, the Hudson River, and into New York Bay in New York. The northwest side of Glastenbury drains into the Fayville Branch of Warm Brook, thence into Batten Kill and the Hudson River.
Glastenbury is the southernmost mountain on the Long Trail, a 272-mile (438-km) hiking trail running the length of Vermont. In this part of the state, the Appalachian Trail, a 2,170-mile (3,500-km) National Scenic Trail from Georgia to Maine, coincides with the Long Trail.