New South Wales Premier Gladys Berejiklian has broken ranks with her ethnic church and declared she will be voting "Yes" in the same-sex marriage postal survey.

Speaking at an event in Sydney, Ms Berejiklian described same-sex marriage as a "no brainer" and one of the most important human rights issues of our time.

The position has put her at odds with her Armenian Apostolic Church, which claims same-sex marriage would pave the way for "radical gay sex education programs" to be taught in schools.

Ms Berejiklian, who was born in Australia to Armenian immigrants, is a regular attender of church events and has been to several this year.

In a Facebook post this week, the Armenian Apostolic Church of Holy Resurrection in Chatswood — where Ms Berejiklain's parents were married — warned followers their faith was "under fire" in the survey.

NSW Premier Gladys Berejiklian attends a memorial service in April. ( Picture: armenianchurchsydney.org.au )

It said redefining marriage would have "consequences" for religious freedom, free speech and children's education.

"Allowing radical gay sex education programs to become widespread and compulsory, where parents can't say no," the post read.

During her speech at the "Parliament Says Yes" event, Ms Berejiklian said she was crossing her fingers the survey returns a "Yes" vote.

"There is no doubt that there are people out there in the community with conservative views, there are people out there with different religious beliefs and faiths," she said.

"We respect all of that, especially with someone like myself with my own personal background."

Church 'has nothing against gays and lesbians'

Nishan Basmajian, the executive officer of Australia and New Zealand Diocese of the Armenian Church, said his organisation respected gay people.

"We are against same-sex marriage," he said.

"We have nothing against gays and lesbians, nothing at all.

"Through our Christian values and Christian education we don't see those values are respected [in same-sex marriage]."

Mr Basmajian said the church did not "mix too much" with politics.

Key dates in SSM postal survey: August 24 — the final day to register with the AEC if you want to take part in the survey

September 12 — survey forms start being sent out

September 25 — all forms are expected to have been sent

October 27 — forms are strongly encouraged to be returned by this date

November 7 — the final deadline to return surveys

November 15 — results are released

"I don't know what the Premier thinks but as a church we adhere to our Christian values," he said.

Ms Berejiklian said voting for same-sex marriage was a simple decision for her.

"I'm hoping that all of us will look back and feel incredibly proud that we were part of something special," she said.

"That we put aside all of our different political views and came together in supporting our colleagues, in supporting our community, in supporting what is one of the most important decisions of our time, I believe, in terms of human rights."

Same-sex marriage survey forms are being distributed to Australians, with final results from the survey to be announced in November.