Hazard has been persistently linked with a move to Madrid and, with his contract set to expire in June 2020 and Chelsea struggling for a top-four finish this season, he could be an attractive target for the LaLiga club at the end of this campaign.
Courtois spent four years playing alongside Hazard at Stamford Bridge, winning the Premier League in 2015 and 2017, and they also reached the semi-finals of the World Cup together last year.
The goalkeeper claimed to be unaware of the situation regarding Hazard's future but revealed he would welcome a reunion at the Santiago Bernabeu.
"It would be nice, of course, but I cannot say much about it," he told VTM Nieuws.
"That is something he has to decide and what Madrid must decide if they want him, because I do not know that either.
"But Eden is a top player and also my buddy, so if he came here it would be fun, but he has to make his choices."
Asked whether he had spoken to Hazard about the possibility of a move, Courtois added: "No, occasionally we laugh at the fact that we like to play football together but that is something I do not interfere in.
"We will see at the end of the season what can happen but Eden is a fantastic football player."
Hazard has already admitted to making a decision on what his next move will be.
He is yet to reveal his intentions to Chelsea, Real and the rest of the world, but has promised that answers are coming.
The 28-year-old told RMC Sport recently: "I know what I’m going to do. I have decided.
"For now, the only thing to think about is playing well for Chelsea.
"I have a year-and-a-half left on my contract, everyone knows.
"My decision will be known soon, but it’s not something that affects my mind.
"I think about it, but without thinking about it. When I’m in the field, I just want to play. We’ll see what happens after."