The 25-year-old Spaniard, who has suffered bouts of illness and injury after climbing to number one in the world in 2003, has spent much of 2005 rebuilding his career after slipping to 92nd earlier this year. He is now ranked 18th.
Ferrero had earlier been confirmed as an entrant for the Auckland Open in New Zealand, which runs from Jan. 9-14, the same week as Sydney. But Sydney organisers said he would play in Australia instead.
"I was delighted to receive the request from Juan Carlos late last night and it was an easy decision to give him the first of the men's wild cards," tournament director Craig Watson said in a statement.
"He has been a great champion and continues to play outstanding tennis."
"All credit to him for the way he has made a comeback to tennis and now be ranked inside the world's top 20."
Ferrero won the French Open in 2003 and also reached the final of the U.S. Open the same year, reaching number one in the world in the process. However a series of injuries to his wrist, ribs and a bout of chickenpox affected his performances in 2004 and his ranking slipped.
In 2005, he made the finals in Barcelona and Vienna and a semi-finalist at Beijing and Monte Carlo.
The Australian Open, the year's first grand slam tournament, begins in Melbourne on Jan 16-29.
