The pair were near the summit of the 4370ft peak, the UK's highest mountain, on an ice climb when the tragedy happened.
Nearby climbers who were also tackling Zero Gully, on the north face, heard screams and called the police.
Lochaber Mountain Rescue Team and a Sea King rescue helicopter discovered the two seriously injured men at the bottom of a 1000ft gully.
They were airlifted to Belford Hospital in Fort William, where the man died.
Northern Constabulary said the other male was being treated for serious injuries.
John Stevenson, the mountain rescue team leader, said: "We got the call around 11am to say two boys had fallen on the Ben. Some climbers alerted the police and we sent in a team.
"We located the two guys and they were airlifted to hospital, but unfortunately one of them did not make it.
"They had been tackling the north face on the Ben, on a classic route known as Zero Gully.
"They fell over 1000ft, which is quite a distance. The other guy is lucky to survive.
"It is another tragedy on the Ben. Hopefully we won't see any more this winter."
The Zero Gully is one of Ben Nevis' three most popular ice climbs near the summit of the peak, along with Point Five and The Orion.
A Northern Constabulary spokesman said: "Shortly before 11am police received a report of two people having fallen a considerable height near the summit of Ben Nevis.
"ARCC (Rescue 137) and Lochaber Mountain Rescue team attended and effected a rescue, however, one of the climbers had died.
"The surviving casualty suffered serious injuries and has been conveyed to Belford Hospital, Fort William."
The man has not been named.
Ben Nevis attracts around 125,000 ascents each year. Last year a 22-year-old Frenchman died after falling ill with hypothermia while attempting to scale the peak.
Last month, the SportScotland Avalanche Information Service warned climbers to be vigilant after new figures revealed there have been 107 reported avalanches this winter, despite low levels of snow.