Jeffers said in a statement about leaving Everton: "It's a great opportunity for me and one I couldn't turn down.
"I'm an Evertonian so it was a difficult decision to leave but Ipswich is a massive club and I'm relishing the chance to help the club get back to where it should be.
"I've been a big admirer of Paul Cook and his work for many years and now to be part of his backroom team is very exciting and I can't wait to get going."
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