However, Mr Turnbull could retain government with the support of independent MPs and minor parties.
Mr Joyce#8217;s father was born in New Zealand and moved to Australia in 1947. The politician was born in the New South Wales town of Tamworth in 1967.
The office of New Zealand Internal Affairs Minister Peter Dunne confirmed to Australian media that under New Zealand law, a child born to a New Zealand national is automatically given citizenship.
Dual citizens are not allowed to run for public office under Australia#8217;s constitution.
PM Malcolm Turnbull#8217;s government risks losing its grip on power if Mr Joyce is ruled ineligible.
Treasurer Scott Morrison, a senior government minister, said it was important not to #8220;leap to conclusions#8221;.
Mr Joyce said he had been advised by Australia#8217;s solicitor-general that he was not in breach of the constitution.