The mishap occurred this afternoon near Mandal on Chamoli-Kedarnath road, about 13 km from here, a police official said.
A Sikh family from Delhi had gone to Balkhila river for a bath in Mandal ghati when the incident happened, he said.
Water level suddenly shot up in the river sweeping away Gyan Singh and his two children.
A Nepali labourer working on the banks of the river saved the two children from drowning, but Gyan Singh could not be rescued, the official said.
Rescue teams have recovered the pilgrim's body from the river.