Johnston arrived at Franklin’s Gardens in 2008 from Sale Sharks, and he has played an important role within the backroom staff that has helped the Saints team reach six finals in as many seasons and establish itself in the Aviva Premiership’s higher echelons.
He leaves by mutual consent and with immediate effect.
“Nick has been an important person behind the scenes over the past few years and I’m sorry to see him leave us,” said Saints chief executive Allan Robson. “He has worked extremely hard to get our performance department into a place where it is the envy of the other Aviva Premiership clubs and at the cutting edge.
“However he now has a young family and wants to take some time to enjoy being a new father.
“I’d like to thank Nick for everything that he’s done at Franklin’s Gardens and wish him all the best for the future.”
Director of rugby Jim Mallinder added: “We’re in a much stronger position than we were five years ago, and a lot of that is down to Nick, who has put in place procedures and practices that will stand us in good stead for the future, both with the first team and with the younger players in the Academy system.
“I’ve enjoyed working with Nick at the Saints, and on behalf of the playing department I wish him all the best for the future, and hope that he won’t be a stranger at Franklin’s Gardens.”
Northampton Saints will make no further comment at this time.