Turnbull, who was also chief executive of the SUFC Trust at Glanford Park, has become head of recruitment and scouting with the Blades where he links up with former Scunthorpe manager Nigel Adkins.
The move sees the rekindling of a successful partnership which saw the Iron promoted twice to the Championship and survival in the second tier in 2009/10.
“We are delighted that Lee is joining us and we are confident that he will prove to be a very important member of our team,” said Sheffield United boss Adkins.
“Lee is very well-known to us and was an integral part of our success at Scunthorpe United. He has a very good eye for a player and will work closely with the existing staff with regards to identifying targets, as well as providing us with information on future opponents.”
Turnbull joins Andy Crosby (assistant manager) and Dean Wilkins (first-team coach) in accepting roles as part of Adkins’ backroom team at Bramall Lane.
A brief statement on Scunthorpe’s official club website said: “The club would like to place on record our thanks for Lee’s tremendous work in his time at the football club; both as chief scout and as chief executive of the SUFC Trust.”
Turnbull, 47, played for Middlesbrough, Doncaster, Chesterfield and Scunthorpe, amongst others, in a lengthy playing career.