Sammy Lee has joined Bolton for a third time during his football career.
The 53-year-old, who finished his playing days with the club in 1991 and was assistant manager and then manager from 2005-07, has now taken up the role of head of academy coaching.
Manager Owen Coyle said: "I know Sammy will bring a great deal of top-level coaching experience and enthusiasm, and that can only be of huge benefit for our youth players."
Young midfielder Josh Vela, meanwhile, has signed a three-and-a- half-year contract extension.
The 18-year-old stood on the brink of a first-team breakthrough earlier this season until fracturing a foot in a reserve game in November.
Now fit again, Vela told the club's official website: "It's been a bit of a frustrating season for me with the injury, so I just want to continue working hard.
"My aim is of course to get into the first team, and I know I've still got a lot to learn, but I feel I am developing into a better player as each day goes by."