A 33-year-old Swiss man died in hospital in Lausanne after being transported there by helicopter following the snow slide at the Pointes de Tsavolire, a 3,026-metre mountain in the Becs de Bosson Alpine region.
A 49-year-old Frenchman died earlier in Sion hospital, Valais cantonal police said.
Both men were part of a ski touring group of five CERN employees who were skiing down the north face of the mountain when a sheet of snow gave way, burying four of the skiers at around 11am on Sunday.
The fifth skier was able to dig out two his colleagues, who escaped with minor injuries, but the two other victims were buried in more than 2.5 metres of snow, police said.
Emergency rescue workers were able to eventually extricate the pair but they were both critically injured.
The Frenchman worked in the engineering department while AFP reported the Swiss man worked with laser beams at CERN, home of the Large Hadron Collider (LHC) — the world's biggest particle smasher famous for identifying the so-called "God particle".
The five skiers had set off cross country early Sunday from the village of Eison for the picturesque Pointes de Tsavolire area, south of Sierre.
"I must say that all CERN people are deeply saddened by this tragic news," CERN spokesman Arnaud Marsollier told The Local.
He said the skiers in the group were accompanied by a guide and were experienced in back country skiing.
"It is with great sadness that we learned that on Sunday April 12th a group of touring skiers from our club were taken by surprise by an avalanche in Valais," the committee of the CERN ski club said in a message in French on its website.
"We have very little information on the circumstances in which this tragic accident occurred," the committee said.
"Our strongest thoughts go to the families and friends of our friends who passed away."
Marsollier told The Local he believed the tragedy was unprecedented for the club.
"As far as I know, we never had such an accident in the past within the CERN ski club — the ski club was founded in 1963."
Experts have warned of the lingering danger of avalanches across the Swiss Alps.
Snow slides in Switzerland have claimed at least 31 lives so far in the 2014-2015 winter season, making it the most deadly year since 2009-2010.