The legendary goalkeeper suffered the stroke while on holiday in a Croatian island and had to be lifted to hospital by a helicopter, De Telegraaf reports.
Van der Sar was admitted to intensive care on Friday afternoon.
Ajax posted a message of support for their former CEO on Twitter, which read: "On Friday, Edwin van der Sar has had a bleeding around his brain.
On Friday, Edwin van der Sar has had a bleeding around his brain. He’s currently in hospital in the intensive care unit and is in a stable condition.— AFC Ajax (@AFCAjax) July 7, 2023
Once there is more concrete information, an update will follow.
Everyone at Ajax wishes Edwin a speedy recovery. We’re thinking… pic.twitter.com/M7jKs5TBB9
"He’s currently in hospital in the intensive care unit and is in a stable condition. Once there is more concrete information, an update will follow.
"Everyone at Ajax wishes Edwin a speedy recovery. We’re thinking of you."
The 52-year-old, who won Champions League trophies with Ajax and United, stepped down from his role as CEO of the Dutch giants over a month ago. He initially joined his former side as marketing director in 2012 before being promoted to chief executive four years later.
Man Utd the following statement on Friday evening: "Manchester United is holding Edwin van der Sar and his family in our collective thoughts after hearing the news that the legendary goalkeeper has fallen seriously ill.
"Edwin always receives a warm welcome whenever he returns to Old Trafford, having been one of the most popular and decorated goalkeepers in our club's history. Between the Dutchman's arrival from Fulham in June 2005 and his retirement from football in May 2011 at the age of 40, he made a total of 266 appearances and contributed hugely to the Reds winning four Premier League titles, the Champions League and Club World Cup, among other trophies under Sir Alex Ferguson.
"Everyone at United wishes to join our friends at Ajax in wishing Edwin all the very best for a full and swift recovery."