The Cairngorm Mountain Rescue was called out at 17:30 to help the walker on the 1,296m (4,252ft) Braeriach.
A dozen rescuers were dropped off by helicopter and then carried out line searches on the summit plateau.
The walker was found at about 23:30 on Friday and was taken down the mountain before being airlifted to safety.
The condition of the casualty is not known.
The rescue team said it was a "demanding" search in "thick mist, driving drizzle and a strong breeze" with visibility dropping to 10m (33ft) even before it got dark.
A team spokesman added: "Casualty was located at 23:30 high on the hill then supported/half-carried across boulder fields down to a pick-up point below the clouds, from which the aircraft took him to safety.
"Thanks are due to [Coastguard rescue helicopter] R951 who came back for the sodden hill parties as well... Made a long night about two hours shorter."
A hillwalker has been rescued after getting lost in thick mist and strong winds on the top of Scotland's third highest mountain.