The former Atletico striker praised the shot-stopper ahead of Colombia's friendly with Belgium, while Thomas Vermaelen hailed the Monaco star's talent
The striker left Vicente Calderon - where the shot-stopper is spending his third consecutive season on loan from Chelsea - for Ligue 1 in the summer.
On Thursday Falcao will clash with Courtois when Belgium host Colombia in a friendly, and the 27-year-old had nothing but praise for his former team-mate.
"He is a good friend," Falcao is quoted as saying by Nieuwsblad. "And he is the best goalkeeper in the world."
Thomas Vermaelen has warned his Belgium team-mates that dealing with the former Porto striker is going to be difficult, but says playing against South American opposition is great preparation for the World Cup.
"Playing against Radamel Falcao is a great challenge," the Arsenal defender said. "Falcao has been a goal machine.
"He plays for the opposition, which makes this game more interesting, especially for the defenders to try to prevent him scoring.
"Ahead of the World Cup, it is a very good idea for us to measure ourselves with teams from other continents."