The 66-year-old former Magpies boss returns to St James Park for a second spell as senior executive in charge of all football-related matters on a three-year deal
The former Wimbledon manager will report directly to the club's board as the senior executive in charge of all football-related matters, working alongside manager Alan Pardew and chief scout Graham Carr.
"The board are pleased to welcome Joe back to the club. Joe has many years of experience working within the game, and this experience will be of great benefit to the club in achieving our objectives over the coming seasons," Newcastle's managing director Derek Llambias told the club's official website.
The 66-year-old, who managed the Magpies in 2008/09 before leaving his position because of illness, revealed his appointment on Sunday before any official confirmation.
The announcement led to criticism from Newcastle supporters, prompting Kinnear to defend his position with a gaffe-strewn rant during a radio interview.
The Irishman had a seven-year management spell with Wimbledon and, as a player, represented Tottenham for a decade while also winning 26 Republic of Ireland caps.