Dr. Richard Fessler said the 52-year-old senator was "completely oriented" and "follows commands very briskly," though he is still listed in serious condition, the Chicago Tribune reported.
"He's doing better than I expected he would be doing at this point," Fessler told reporters at a news conference at Northwestern University in Chicago.
Kirk's breathing tube has been removed and he was medicated with a light sedative. He has some left-side facial paralysis that causes his speech to be slurred and is moving his left side "very little," the neurosurgeon said.
"He asked for his BlackBerry yesterday," Fessler said. "I'm very happy with his progress and where his condition sits right now."
Kirk's recovery will be "a long process" that includes therapy.
Part of Kirk's skull was removed early Monday to relieve pressure caused by swelling on the right side of his brain, Fessler has said.
Politico reported Fessler said Kirk was in good overall physical condition before the stroke.
"I don't think this event had anything to do with either stress or diet," the doctor said. "It's just one of those unfortunate disasters that happens to people sometimes."
The Washington publication said it will be months before the Illinois Republican goes back to work in Washington.