The guide was accompanying two clients in a climb of the 4,300-metre high Grand Combin peak, cantonal police said.
The trio left the Panossière mountain hut at 2,645 metres early in the morning and began to cross the glacier on skis in their bid to reach the summit, police said.
But shortly after 6am a “snow bridge” gave way beneath the guide’s skis and he fell 20 metres.
Emergency rescue workers transported by an Air Glaciers helicopter arrived at the scene but the guide was already dead, police said.
The guide was from the canton of Graubünden.
He is at least the third mountain guide to die in the Valais Alps since the beginning of the year.
Last month, a 35-year-old guide died in a helicopter skiing accident near Zermatt along with the 39-year-old German woman.
Another mountain guide, Samuel Matthey-Doret, 28, died with three others after being swept away by an avalanche in early January in the Mase-Val d’Hérens region.
Matthey-Doret was leading an avalanche course at the time.