The fire broke out around noon Sunday at the Edgewood Rehabilitation and Living Center in Farmington.
Investigators said a resident called 911 after smoke started to fill his bathroom.
Firefighters said flames then began to spread into neighboring rooms.
Ten other departments had to be called in to get things under control.
There were no serious injures.
"We had one minor injury and that was just in evacuating the patients from the facility. And everybody did their job today and we got a good outcome," said Sgt. Scott Richardson with the Maine State Fire Marshal's Office.
The building does have extensive water damage.
The nursing home residents were taken to Mt. Blue High School while officials worked out places for them to stay overnight.