The former Netherlands international lavished praised on the Ajax skipper, and believes he has what it takes to succeed at the Spanish giants and become as good as Jaap Stam
The Belgium international is continually being tied with a move away from Ajax, and has been linked with Arsenal, Tottenham Hotspur and Juventus in recent weeks.
De Boer is confident that Vertonghen has the attributes to succeed with the two Spanish giants and believes that he is even better than Thomas Vermaelen, who left Ajax for Arsenal in the summer of 2009.
"Vertonghen would fit in very well at Real Madrid or Barcelona. He's always calm on the ball, and knows when to move into midfield. I'm 100 per cent sure that he would succeed there," De Boer said to NUsport.
"He has what it takes to become as good as Jaap Stam. Just look at Vermaelen. He was a decent player during his spell at Ajax, but is now seen as one of the best defenders around in the Premier League. And Vertonghen is better than Vermaelen."
Vertonghen has a contract with Ajax until the summer of 2013, and is widely expected to bid farewell to the Eredivisie champions at the end of the season.