The Spain international has been on the sidelines since breaking a bone in his hand on January 20, but Jose Mourinho has named Casillas in Madrid's squad to face Manchester United in the Champions League on Tuesday evening.
Van der Sar has hailed the impact Casillas has made for both club and country since making his debut in 1999.
"What can we say about Casillas? He is 31-years-old and has won everything," Goal.com quotes the Dutchman as saying.
"I think he started playing for the first team of Real Madrid at the age of 17 or 18, that says everything. He has been wonderful for all this time for both Real Madrid and the Spanish national team.
"I do not know him personally, but I see him, I read his interviews, and I've never heard anything bad about him. He's a great captain for Real Madrid and for Spain."
Casillas has made 29 appearances for Real Madrid this season.