David Johnston has taken up the role, which was first flagged in the Defence Export Stategy released earlier this year.
Johnston held the role of Minister for Defence from September 2013 until late December 2014. Minister for Defence Industry Christopher Pyne said Johnston's experience will be pivotal in his new role.
"This appointment will greatly expand the government’s reach in promoting Australia’s world class defence industry," Minister Pyne said.
"As a former minister for defence, Mr Johnston brings a wealth of experience and knowledge of Australian defence industry to this significant role."
Minister Pyne said the appointment of a defence export advocate would build on his and the government's advocacy efforts.
"I work tirelessly to advocate for Australian industries looking to sell their world class defence materiel to our friends and allies but I can’t be everywhere," the minister said.
"Our defence export advocate will help connect Australian industry to overseas governments and defence forces, build relationships in our key markets and act as a focal point for long term campaigns."
As the first Australian defence export advocate, Mr Johnston will also work closely with the Australian Defence Export Office to provide senior advocacy.