The winger has agreed a deal that will see him make the switch to Ewood Park from Spurs until the end of the season.
Bentley joined Rovers from Arsenal in 2005 and put himself on the map the following January with a brilliant hat-trick in a 4-3 defeat of Manchester United.
It was the highlight of a season which saw Blackburn finish sixth to qualify for the UEFA Cup.
Bentley's fine form continued in the following campaign, leading to an England call-up before Spurs swooped to sign him in the summer for £15million.
The 28-year-old has slipped well down the pecking order at White Hart Lane in recent years, with loan spells at Birmingham, West Ham and Russian side FC Rostov.
Bentley, who has been allocated the No 35 shirt, is eligible to play in Saturday's FA Cup fifth round tie with Arsenal at Emirates Stadium.