The Scottish striker has signed a four-and-a-half-year deal with Boro, joining the promotion-chasing club from Blackburn Rovers for an undisclosed fee.
25-year-old Rhodes scored 85 goals in 169 appearances during his time with Rovers which came after a prolific spell at Huddersfield Town.
This season, Rhodes has netted 10 Championship goals for Blackburn but will not be looking to fire Boro to an automatic promotion to the Premier League.
CONFIRMED | The club is delighted to announce the signing of Jordan Rhodes from @OneRovers - https://t.co/oe6r5ytZYGpic.twitter.com/aRvEQUXukG
— Middlesbrough FC (@Boro) February 1, 2016