Colorado Division of Wildlife spokesman Randy Hampton said the man had gone to the first floor of his home to check on his three barking dogs when the bear struck him in the head.
Hampton said the man did not suffer life-threatening injuries and was being treated at a local hospital. Wildlife officers are expected to talk to the man Friday morning. Hampton said it's unknown how the bear entered the home.
Wildlife officers are searching for the bear in the neighborhood and have set up a trap in the area. The bear will be euthanized when it is found.
"These are large, powerful animals. You certainly don't want to end up in this situation, especially in your home," Hampton said.
Wildlife officers in and near the resort town about 200 miles west of Denver have killed at least nine bears so far this summer because of their aggressive behavior. Area police have responded to about 200 bear sightings in August, up from 16 last August.
Hampton said "it's been incredibly frustrating" for wildlife officers to have to deal with the increased bear activity and have to euthanize the animals because people are not disposing of trash and storing food properly.
In addition to trash, Hampton said an abundance of fruit and crabapple trees in Aspen are also attracting bears. He said bears are particularly active now because they are preparing for hibernation, consuming about 20,000 calories a day and spending 20 hours a day eating.
The man's name was not released.