Rafa Benitez makes key appointment at Newcastle, goalie coach tweets fans
Antia replaces Fabio Pecchia, who has left to become manager of Hellas Verona.
The 43-year-old Spaniard – who played under Benitez at Real Madrid's academy and Valladolid – had been working at the Aspire Academy in Qatar.
Rafa Benitez said: "I am delighted that Mikel is joining my staff.
"He is a very talented coach, and I know he will add great expertise to my team.
"At the same time I am sad to see Fabio depart as he has been an excellent professional from the first day until the last in the years we have worked together.
"He leaves to face these new and exciting challenges, both personally and professionally. I wish him all the best and say thank you."
The rest of Rafa Benitez's coaching staff – Francisco de Míguel Moreno, Antonio Gómez Pérez, Ian Cathro and Simon Smith – are staying at the relegated club.
Smith said on Twitter: "Delighted to be staying."