The former Sheffield United, Queens Park Rangers, Leeds United and Bury shot-stopper will also register as a player so he can act as goalkeeping cover.
Kenny is a former Blades team-mate of Town boss Rob Page, who is delighted to have captured the 38-year-old.
“Paddy will be a fantastic addition to our staff,” said Page.
“He is a very experienced goalkeeper who has a wealth of knowledge to pass on and I know the keepers here will benefit from his work.
“We played together at Sheffield United and I know all about the qualities he brings and the experience he can pass on.
“There aren’t many keepers with his depth and range of experience and with his energy and enthusiasm I think he will be a fantastic influence to our keepers.”
New loan regulations for season ahead mean emergency loans are no longer allowed, and in a smart move, Page will register Kenny to be the third goalkeeper in his Cobblers squad.
Kenny will be a back-up to Adam Smith and Ryan Clarke, and Page said: “Paddy will also be registered to play for us if required as he is still a high class keeper.
“He has kept himself fit and sharp but his main role will be to coach, but having three goalkeepers is always going to be an advantage with the new loan regulations.”
Kenny has made more than 600 senior appearances in an 18-year playing career.
He ended last season on loan at Rotherham United, but hasn’t played since December, 2014, when he played for Oldham Athletic.
Kenny began his Football League career at Bury, once being sent off against the Cobblers at Gigg Lane in November 2001, and then moved to Bramall Lane where he played more than 300 games for the Blades, and spells at QPR and Leeds followed. He also played seven times for the Republic of Ireland national team.
Kenny’s appointment means that Carl Muggleton has left the club.
Muggleton was the goalkeeping coach under previous manager Chris Wilder, but has now moved on after his contract expired.