Earlier this month, Reporters without Borders (RSF) said it condemned any measures taken to censor websites or news media which had published the material.
According to a report on the RSF website, the mirror site will be launched tomorrow at wikileaks.rsf.org, but it already appears to be available.
The organisation said it is hosting the site as a "gesture of support" for the WikiLeaks.
"This is a gesture of support for WikiLeaks' right to publish information without being obstructed," it said in a report.
"We defend the free flow of information on the internet and the protection of sources, without which investigative journalism cannot exist."
But it added the partnership will be "constantly reassessed" based on the future activities of WikiLeaks.
"We are doing this solely as part of the partnership that WikiLeaks has established with news media," it added.
According to WikiLeaks more than 2,000 mirror sites have been set up across the world at the time of writing, amid claims the main site is under "heavy attack".