Just after midnight the farmer found the barn full of chickens on fire, Graubünden police said in a statement.
Fifty firefighters attended the scene and extinguished the blaze at 2.30am.
However all 2,000 chickens in the barn were killed.
Police have opened an investigation to find out why the fire broke out.
The blaze is the latest of several in the country lately that have caused the deaths of animals.
And at the end of the month 50 cows were killed in two fires at farm building in the same area.