Hills, 34, and Siddons, 39, who both enjoyed decorated careers at Australian domestic level, will begin work in their new roles later this month.
CA said both coaches, based at the academy's training set-up in Brisbane, will take turns on a series-by-series basis at filling the assistant coach and performance analyst role with the Australian team.
The positions became vacant earlier this year with the elevation of former national assistant coach Tim Nielsen to be the head coach of the academy.
In June, either Hills or Siddons will remain at the academy to work with the country's rising young talent, while the other will travel to England with the Australian One-day International and Test squads.
"After a detailed review of the coaching structures in place both at the academy and with the Australian squad, it was decided to try and bring the two entities closer together and enhance the information flow," CA chief executive James Sutherland said in a statement on Monday.
"Ideally, this move means that the expert knowledge gained out on the road by the Australian team can be filtered back to the state associations and our next batch of stars, and that the developments being made at the academy can help enhance the Australian teams ongoing performance."
Hills, who made 112 first-class appearances for Tasmania between 1991-92 and 2001-02, has been an assistant coach with Tasmania since 2003.
Siddons has been South Australia's assistant coach since October 2002, following an outstanding career during which he captained Victoria and South Australia.
He played 160 first-class matches for both states between 1984-85 and 1999-00 and his career runs in domestic first-class cricket (10,643) was for a time an Australian record.
Australian coach John Buchanan said Hills and Siddons would provide him with added support.
"Both Dene and Jamie are multi-skilled individuals, and that's just what we wanted when we were looking to fill this position," Buchanan said.
"This is an innovative approach to the role, meaning we can take advantage of the great qualities both men can bring to it."