The 52-year-old returns to his hometown club after eight years working with England’s development teams across various age groups.
Smith originally left the Magpies in 2004 after an 11-year period when he worked under Ruud Gullit and Sir Bobby Robson and he will now link up with the recently-appointed Steve McClaren at St. James' Park.
Simon Smith previously worked at Newcastle United under Sir Bobby Robson
"On behalf of The FA and especially the goalkeeping department, I would like to thank Simon for his contribution over the last eight years," said Martin Thomas, The FA's national goalkeeping coach.
"Simon has been a fundamental part of the provision for the development of goalkeepers and goalkeepers’ coaches at all levels of the game. It is a fantastic opportunity for him to return to work for the club closest to his heart.
"I know he’s a massive supporter of The FA and I’m sure there will be a time where we can once again call on his vast experience and knowledge. But in the meantime, I’d like to wish Simon good luck on behalf of everyone at The FA."
Gareth Southgate, head of national teams at The FA, added: "We’d like to wish Simon all the very best for the next chapter of his career at Newcastle United.
"He has been a great servant to The FA and we thank him for all of his efforts over the last eight years."
