The Scot spent seven months working with his compatriot during his first spell in charge.
前者 スコットランド international midfielder, who spent seven months with Moyes during his first spell as Hammers boss, had been working as Michael O’Neill’s assistant manager at Stoke.
He joins Moyes’ team of assistants – Kevin Nolan, Paul Nevin, Stuart Pearce and Xavi Valero – as he finalises his staff after signing a new three-year contract, と Nick Davies also returning to the fitness and sports science set-up.
Moyes told the club’s official website: “I’m delighted to welcome back both Billy and Nick.
“They bring a wealth of experience and expertise to the team, they know the football club well and they will fit straight back in to how we work.”
The Hammers have also revealed they are close to appointing a head of recruitment as they attempt to build upon last season’s sixth-place finish.
Moyes added: “It was very important to me that we did this together.
“The progress so far at the club has been a real team effort and my staff, not just the coaches, have been a crucial part of that.
“We are looking to continue to build on what we have done so far and we will work to keep our levels high.”