Prime Minister Malcolm Turnbull has chosen a new secretary of the Defence Department: his current chief of staff, Greg Moriarty.

More than two months have passed since widely respected and long-serving bureaucrat Dennis Richardson stepped down as head of the Defence Department.

Mr Moriarty is a former ambassador to Indonesia and Iran and was Australia's first anti-terrorism coordinator.

He has worked as an intelligence analyst and as a senior negotiator with the Peace Monitoring Group in Bougainville.

Mr Turnbull said his new chief of staff would be Peter Woolcott, who is currently Australia's high commissioner to New Zealand.

He said Mr Moriarty would bring "a considerable range and depth of experience to the role".

"In August 2016, he joined my office as international and national security adviser and later became my chief-of-staff," Mr Turnbull said.

"I thank Mr Moriarty for his outstanding work in my office, in which he demonstrated his leadership and strategic understanding as he has done throughout his career.

"I also thank Brendan Sargeant for his dedicated service while acting in the role of secretary of the Department of Defence."

Mr Turnbull sought advice from Cricket Australia's chairman David Peever before making the announcement.

Mr Moriarty has been appointed on a five-year term.