The midfielder has signed for United from Ajax and penned a five-year deal with the Red Devils.
Van der Sar, who played for United and won many important trophies during his time at the club, only had good things to say about the departing van de Beek.
On social media, Van Der Sar wrote: “Take care of him, @ManUtd! heartemoji #DreamLikeDonny" and linked to a goodbye tribute video from the club to the player.
Van der Sar has always spoken warmly about United, a club with which he won the Premier League and Champions League.
Van de Beek will be hoping to enjoy similar success in the coming seasons with manager Ole Gunnar Solskjaer's team.
Take care of him, @ManUtd! #DreamLikeDonnyhttps://t.co/AwhwkiI2pQ
— Edwin van der Sar (@vdsar1970) September 2, 2020