A dozen full-time members of the Canadian army will join the search for a Canadian man missing in the New South Wales Snowy Mountains.

Prabhdeep Srawn, 25, was last seen on May 13 when he left Charlotte Pass Village on a walk to Mount Kosciuszko.

Extensive land and aerial searches have failed to find any trace of him, and a police search operation has been scaled back.

Now, 12 off-duty Canadian army personnel will join the search on Sunday. They will be in Australia for about two weeks.

Mr Srawn's sister, Mandeep Srawn, says the men will be equipped with snow and climbing gear and plan to camp in the mountains during the search.

"I think they are expecting it to be colder than it is though. It's not as cold as it gets in Canada," she said.

Mr Srawn's family has offered a $100,000 reward for anyone who finds him.

"These men that are coming from overseas aren't looking after that. They just want to find their fellow soldier," Ms Srawn said.