The 26-year-old stunner, who in the US is best known as a Victoria's Secret lingerie model and Orlando Bloom's squeeze, says she decided to go 'au naturel' to raise awareness of the environment, specifically koalas, reports News.com.au.
"I feel strongly about the need to protect our natural environment because it supports our life -- it really is that simple," Kerr tells the magazine.
Kerr shot the cover for Rolling Stone's first 'green issue' in Sydney in January.
The man behind the lens was photographer Carlotta Moye.
The day-long shoot also included a real koala named Koral, as Kerr is the face of the Australian Koala Foundation's 'No Tree, No Me' campaign.
The campaign aims to protect koalas' natural habitat.
"It's a sad thing -- there are only about 100,000 koalas left in Australia," Kerr said.
"Something like 80 per cent of the koalas' habitat has been destroyed since Europeans arrived in Australia," she added.
Photograph: Cover of Rolling Stone magazine