Rhodes has signed a four-and-a-half year contract with Middlesbrough after joining from Ewood Park.
The Scotland international arrives for an undisclosed fee, believed to be £9million.
Rhodes has scored 11 goals for Blackburn this season.
CONFIRMED | The club is delighted to announce the signing of Jordan Rhodes from @OneRovers – https://t.co/oe6r5ytZYG pic.twitter.com/aRvEQUXukG
— Middlesbrough FC (@Boro) February 1, 2016