Whilst with Bath, Sleightholme won 12 international caps between 1996 and 1997, scoring four tries before leaving the west country side and joining the Midlands club for whom he made 85 appearances.
Starting his career at Yorkshire club Wakefield, Sleightholme joined Bath and made his England A debut in 1995. The following year he made his full Test debut against France in the 1996 Five Nations and represented England the following season, his most memorable contribution two tries against Ireland in Dublin in 1997.
For the past two-and-a-half years, Sleightholme has also been fulfilling a dual role at Northampton as its sponsorship manager, as well as training and playing alongside the professional squad, but has now been offered a new job.
He will, however, remain registered with the club so Saints could call on him in an emergency.
Sleightholme said: “This was a difficult decision to make, particularly during the middle of the season. However, I have a reached a time in my career when I could not afford to turn down an opportunity like this one. I have had a wonderful career spanning 13 seasons and I will take away lifelong memories and friends from Wakefield, Bath and, primarily, Saints.
“The support I have had from the players, management and fans during the last six years at Saints has been second to none in my career, which has made the decision to retire even harder.
“But I fought back from injury two years ago to give myself the opportunity to be able to sign off my career in the way that I wanted. I wanted it to be my decision to retire rather that a decision that was forced upon me through injury,” he added.
Northampton Saints operations director John Steele said: “Jon has been a loyal and committed Saint, and both Jon and his wife Julie have contributed hugely to club life and we wish them all the best of luck.”