The 20kg stray is thought to be a cross between a Tibetan mastiff and a Himalayan sheepdog.
She bounded up to climbers from the Kathmandu-based Summit Club when they were already at a height of 17,000ft and latched on to Don Wargowsky of Seattle.
He said the expedition Sherpas at first only tolerated the dog, but then began to appreciate her climbing ability.
"They'd never seen anything like this happen. They said she was a special dog, that she brought luck to the expedition," Wargowsky said. "Some even thought she was blessed."
At one point Mera spent two nights sleeping out exposed on a glacier leading Wargowsky to fear she would die of cold. But she seemed unharmed and later shared his tent and ate his food.
On the day of the final ascent, he said she seemed unconcerned by the altitude or precipices on either side and bounded ahead of the group.
"I have no clue if she'd been up there before, but she seemed very confident in what she was doing," he said.
She ran ahead of him on the final ridge approaching the summit and waited for him panting with her tongue out, he said.
"I'd never been on top of something like that with a dog. She was leaning up against me and wanting to be petted. It was pretty surreal."
Mera now lives with the expedition's base camp manager, Kaji Sherpa, he said.