The incident happened at a fly-in mineral exploration camp near Wolf Lake about 60 kilometres north of Swift River in the southern Yukon.
Ryan Hennings, a Yukon government conservation officer, said the two-woman crew had observed a sow and two cubs almost three weeks earlier but they'd seen nothing since until the incident late Thursday morning.
Hennings said it was a surprise encounter for both the woman and the bear, which began when she heard her dog bark to alert her.
The bear was about 20 metres away when it charged her, and she tried to pulled her backpack over her head to protect her neck and skull.
"As she was pulling the backpack over her head, the bear swiped at her and caught her in the arm and she's got two large claw wounds, like deep scratches, in her arm and a third one in the back of her elbow,” he said.
“So she was knocked to the ground. The bear kind of hoofed and hawed for a really brief second and then turned around and left."
The bear gathered her cubs and vanished.
Hennings said the worker's partner was on an opposite slope and witnessed the brief encounter, before running to help.
They called their employer via satellite phone. Company officials and conservation officers then flew in by helicopter.
The injured worker received treatment at Whitehorse General Hospital.
Hennings said there's no risk to the public and the bear will be left alone.