The appointments will replace judges who have retired or resigned from the registries in Melbourne, Sydney, Adelaide and Newcastle.
Senator Brandis announced barrister Mark Kranz Moshinsky QC will join the Melbourne registry of the Federal Court on 2 November, replacing Justice Michelle Gordon who has been appointed to the High Court.
Mr Moshinsky has been a barrister in Victoria since 1995 and was appointed senior counsel in 2007.
At the Federal Circuit Court level, Senator Brandis said the new appointees brought a “wealth of experience across a wide range of expertise and will significantly strengthen the Federal Circuit Court”.
In his 2014-2015 annual report, Federal Circuit Court Chief Judge John Pascoe warned the court was struggling to cope with the retirement of nine judges in 12 months.
“Not all of these retiring judges have been replaced,” he said.
“These delays in appointments have had a significant effect on the court's capacity to deal with matters expeditiously, and waiting times for trials have increased significantly.”
Barrister Joshua Douglas Wilson QC will also join the Melbourne registry of the Federal Circuit Court on 2 November, replacing Judge Jeffrey Turner.
Dr Wilson, who holds a Masters of Law and Doctor of Philosophy, was admitted to practice in 1983 in the Supreme Court of Victoria and was appointed senior counsel in 2008.
In Adelaide, Timothy James Heffernan will take the seat of Judge Stuart Lindsay on 23 November.
Having been admitted in 1990, Mr Heffernan acted as a solicitor and prosecutor with the South Australian DPP between 1996 and 2010 before going to the Bar.
The Newcastle registry will gain Steven Charles Arnold Middleton, who has been a barrister in private practice since 2007, on 9 November.
Previously, he served as managing partner of Griffiths Parry Lawyers.
Philip Dowdy will be sworn in at the Sydney registry on 7 December.
Mr Dowdy has practised at the Bar since 1978, with a specialisation in banking, equity and commercial law.