The Belgium international is contracted to the Blues despite being yet to make his competitive bow for the club.
Chelsea snapped him up from Genk in 2011 after spotting his potential early.
They have since allowed Courtois to agree three season-long loan deals at La Liga outfit Atletico Madrid as his route to the first team at Stamford Bridge is blocked by Petr Cech.
The 21-year-old is held in high regard by the Blues, though, and they have no intention of letting him leave on a permanent basis.
Mourinho has moved to reiterate that stance amid reported interest from Barcelona - with the Catalan outfit in the market for a replacement for Victor Valdes, who will not be extending his contract at Camp Nou.
Mourinho said: "We have the best goalkeeper in the world (Cech) and the best young goalkeeper in the world (Courtois). It's a very good problem.
"Our goal is safe and financially we are also very safe - the value in the market is the value of the best.
"In this moment I don't think about it. It doesn't worry me because our situation is fantastic and everything is under our control.
"We control the situation, not Barcelona, Atletico or another team interested in our goalkeepers. We control the situation, so that's fine."