An advance party of about 85 Australian and New Zealand troops left Australia yesterday for Camp Taji, just north of Baghdad, in a joint training mission now called Task Force Taji.
The remainder, about 385, will be deployed in stages over the next month.
The New Zealand Defence Force has asked the Government not to reveal the specifics of the deployment, according to Prime Minister John Key, a request he has met.
All he could say yesterday was that the first group of Kiwis would be leaving "soonish".
The Australian Government and Defence Force is giving more information to the public.
The aim of the non-combat two-year mission is to help train Iraqi troops in their fight against Isis.
But it is also clear from comments by Australian Prime Minister Tony Abbott and US President Barack Obama in recent days that the coalition helping Iraq hope a strengthened Iraqi Army will mean less reliance on Shi'ite militia and on Iranian forces which have helped in the retaking of Tikrit city.
"I think the stronger the Iraqi regular Army is," said Mr Abbott in a press conference "the less likely it is that Shi'ite militia will play a continuing role in the ultimate retaking of the country.
"By strengthening the Iraqi Army, we are giving the Iraqi Government a whole lot of options that it may not currently have."
President Obama hosted Iraqi Prime Minister Haidar al-Abadi in Washington this week in his first visit since taking power last September and Mr Obama said fighters supporting Iraq should respect its sovereignty.
Foreign assistance to Iraq needed to be not only co-ordinated with the Iraqi Government but answerable to it through a clear chain of command.
Mr Key and Defence Minister Gerry Brownlee farewelled New Zealanders from Linton Army Camp last week en route to Australia for training.