O'Boyle had been working as head of elite performance at the Premier League, where he was responsible for advising clubs on talent identification and recruitment.
He has also previously worked as an academy coach for Man United, in addition to having roles with Liverpool, Coventry City, Wrexham and England Under-21s.
O'Boyle will provide support to football director John Murtough, who has said that the club are "delighted" to "welcome Andy back to Manchester".
"We are delighted to welcome Andy back to Manchester United to take up this important role in the club's leadership," Murtough told the club's official website.
"Andy has experience across all technical areas of football, from fitness and sports science to scouting and recruitment. This will make him a valuable addition to my team at Carrington as we continue to strengthen leadership and strategic planning across all our football activities."
According to Sky Sports News, O'Boyle was also responsible for 'performance analysis, sports science and medicine, psychology, and loan management' in his role for the Premier League.
The former Man United academy coach has revealed that he is "thrilled" to be heading back to Old Trafford.
"I am thrilled to be rejoining Manchester United at such an exciting time for the club, as the first team prepares for a fresh start under Erik ten Hag, and the Academy and women's teams go from strength to strength," he said.
"Whilst it has been a privilege to serve the Premier League for the past five years, I can't wait to get started at United and play my part in creating the right environment for football success."
Man United have made huge changes this summer, with Ten Hag also arriving as head coach, while Steve McClaren and Mitchell van der Gaag have been appointed as assistants.
The squad will also be overhauled in the coming months, as Paul Pogba, Nemanja Matic, Jesse Lingard, Juan Mata and Edinson Cavani prepare to leave the club on free transfers.
Meanwhile, Dean Henderson, Phil Jones, Eric Bailly, Axel Tuanzebe and Anthony Martial could all be on their way out of the club during this summer's transfer window.
There will be money, potentially in the region of £120m, to improve the squad, and a new centre-back, central midfielder and centre-forward are likely to arrive.
However, one of the club's leading targets, Frenkie de Jong, has revealed that he wants to remain at Barcelona this summer amid interest from the 20-time English champions.