Despite being miles from home, members of the defence force overseas are close in the thoughts and hearts of Australians this Christmas, Malcolm Turnbull says.

In the prime minister's message to ADF personnel, Mr Turnbull pays tribute to those who serve their country and who have died in that service.

Reflecting on his visit earlier in the year to Iraq and Afghanistan, he praises their courage, professionalism and good humour in a very tough and dangerous environment.

"This Christmas many of you will be far from family and home, but you will be closest of all in our thoughts and in our hearts," he says.

"We are grateful for your sacrifice, and the sacrifice your families make especially at this time of year."

He said that in 2016 the ADF had delivered a compassionate, humanitarian response to tropical cyclone Winston in Fiji, continued maritime security operations in the Middle East and continued to assist in UN operations in South Sudan.

Air Force missions over Iraq and Syria have also provided critical combat support in Iraq's fight to defeat the Islamic State group, Mr Turnbull says.

"So at Christmas, it is with the deepest respect and admiration that I thank you - the men and women of the ADF - for your service in 2016.

"And we know that in this Anzac centenary year, we best honour the diggers of 1916 by supporting you, the servicemen and women, and the veterans and your families of 2016."