Sportal.co.nz 30.Dec.2012Getty Images
The 48-year-old former All Blacks' boss joined the Aviva Premiership club at the end of November, having previously worked for them on a consultancy basis, as the Sharks battle to avoid relegation from the Premiership.
Mitchell guided the club to just their second league win of the season against Worcester on Friday night, but Sale have confirmed he has left his role, leaving Steve Diamond, Bryan Redpath and Pete Anglesea to lead the Sharks battle against the drop.
Owner Brian Kennedy said in a statement: "John was brought in on a consultancy basis with a view to the possibility of being employed in a longer term position within Sale Sharks.
"He has had to return to South Africa for personal reasons which we respect. We are grateful for his valuable and insightful contributions albeit for a shorter term than envisaged.
"Steve Diamond, Bryan Redpath and Pete Anglesea will continue to coach the side, implementing many of John's ideas, and building on last night's excellent performance."
Despite their win over Worcester, Sale remain rooted to the foot of the Premiership table, a point below London Irish.
The summer recruitment of the likes of Scotland lock Richie Gray and England first five-eighths Danny Cipriani had raised hopes of a strong campaign.
But a terrible start to the season saw Redpath, who had joined the Sharks from Gloucester during the latter stages of last season, removed from the position of director of rugby and shifted to that of head coach at the end of October.
As a result chief executive Diamond took over the running of first-team affairs before Mitchell, who had previously been named as part of the club's new rugby strategy management board, arrived to effectively take over the director of rugby position.
Under Mitchell, who left the Golden Lions to join Sale after being cleared of misconduct charges by the South African club, the Sharks had shown signs of improvement but they must now fight to retain their top-flight status without him.