Juergen Kanzian, 41, was attempting a solo climb of North America's tallest peak and was last spotted on Monday ascending Denali Pass, a notch at about the 18,000-foot level of the 20,320-foot peak, officials said.
Other climbers notified park rangers when he had not returned to his camp at the 17,200-foot level by Tuesday night.
Kanzian, a mountaineering guide in the Alps, had told other climbers he intended to ski down after he reached the summit, park officials said.
Denali Pass is a sometimes-treacherous spot in the route up McKinley, the site of many fatal falls. This summer, three people have died in the area, including a guide leading a roped party.
Climbers still on the mountain were keeping their eyes peeled for signs of the missing Austrian, said Maureen McLaughlin, a Denali spokeswoman.
Rangers have found no sign of him despite a search on the mountain by aircraft in which they took hundreds of high-resolution photographs, officials said.
Normally, climbers take eight to 16 hours to reach the mountain's summit and return to the 17,200-foot high camp, McLaughlin said.
Kanzian might have been slowed by new snow that fell on the mountain, but he also had the advantage of traveling by skis, she said.
"Generally, in 24 hours the other climbers would have expected to see him, and they did not," she said.
The McKinley climbing season generally runs from late April to mid-July. There were 250 people on the mountain as of Thursday, McLaughlin said.
A group of climbers who checked in with park rangers and flew to base camp on Wednesday were believed to be the last climbers this season to attempt the peak, she said.
Including that party, 1,205 people have attempted to climb McKinley this year, she said.
Five climbers have died so far this year on McKinley, and three others were killed in accidents on nearby peaks in Denali National Park.