The 33-year-old striker has been out of contract at Cardiff since the end of last month and new Rovers boss Paul Ince is offering the former England forward a chance to prove his fitness by training with the squad during their training camp in Germany.
"Late on Thursday night Robbie Fowler informed us that he had been offered the opportunity to join Blackburn Rovers," a statement on the officialCardiff City website said.
"We fully understand that the lure of the Premier League was a major factor in his decision and we wish Robbie well in the future at his new club."