Goalkeeper Van der Sar, 38, announced in June this would be his final season. But Manchester United boss Ferguson has told the Dutch ace he will keep the No1 shirt for next campaign.
Fergie also gave Van der Sar the option to sign up for another season after that. It was only the guarantee that he would still be first choice next campaign that convinced the Dutchman to continue.
It had been thought that England international Ben Foster would get his chance next season but he may now look to go on loan next season or even leave.
Van der Sar has enjoyed a glittering career starting at Ajax where he won four titles and the Champions League in 1995. He moved on to Juventus and then Fulham before joining United in June 2005.
Ferguson has since described him as the best goalkeeper the club has had since Peter Schmeichel.
Van der Sar — who has played over 160 games for the Reds — will go down in United legend for his sudden-death penalty save from Nicolas Anelka that won last season’s Champions League against Chelsea.