The fire happened just before 2 p.m. at 107 Elliot Street, the fire department said. Crews found a fire contained to a single apartment on the sixth floor of the building.
The sprinkler system put the fire out but caused significant water damage to 17 additional apartments, according to the fire department.
Two people suffered minor injuries and were evaluated at the scene before being taken to a nearby hospital, the fire department said.
Brattleboro emergency crews received assistance from Chesterfield Fire, Keene New Hampshire, Guilford Fire and other nearby units.
Multiple people were displaced from their apartments because of the water damage, the Brattleboro Fire Department said. The American Red Cross and the Brattleboro Housing Authority are providing temporary housing solutions and support services.
Restoration efforts are underway in the damaged units. The cause of the fire remains under investigation.