The information sheet makes clear it will take "several years" for asylum seekers to be potentially resettled and there's no guarantee even then they'll make it to Australia.
The sheet urges asylum seekers to "remember you can decide to leave Nauru voluntarily at any time".
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"Overall you can expect it may take several years, from when you first arrived in Nauru, to being potentially resettled," it states.
"It is possible you could be resettled in a country as part of broader regional arrangements.
"You can also return with a package of assistance to help you re-establish yourself in your home country."
Detainees are told they are no longer entitled to bring immediate family to Australia using refugee or humanitarian visas even if eventually granted a protection visa.
Refugee advocate Pamela Curr says the letters are "all about pressing people to go home".
"They're telling them it's going to take years, they're never going to see their families again and they've got little chance of being resettled in Australia," Ms Curr told AAP on Friday.
"It is a form of bullying.
"These people are stuck out there in tents on the equator standing knee-deep in water and if that's not bad enough they're being told they have got Buckley's chance of ever getting out of it."
Ms Curr said in the past Australia offered refugees protection but now Canberra persecuted them.
She said the harsh treatment wouldn't stop the boats "because we can never be worse than the Taliban in Afghanistan or the Sri Lankan white vans".
Immigration department spokesman Sandi Logan on Friday defended the information sheets.
"It's rather disingenuous if people are criticising the department for keeping its clients fully informed," he told ABC radio.
"We'd be criticised if we didn't."
Mr Logan said the department was "duty-bound" to provide the information.
