The role will see Leadbitter work with players right across the age groups at the club where he made 230 appearances and where he is still revered for his role in the club's promotion to the Premier League in 2016.
Leadbitter completed his UEFA A licence last year as he worked closely with Middlesbrough, and has now made that move permanent.
Middlesbrough's academy manager Craig Liddle said: "It’s great to have someone with Grant’s experience on board. He’s worked hard on his coaching qualifications over the past year and he brings a wealth of knowledge and understanding.
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“He’s an example for the young players in our Academy because of what he achieved in his career and he knows what it takes to be a good professional.”
Leadbitter made over 200 appearances across two spells as a player at Sunderland, his boyhood club.