The LaLiga club had agreed to sign Endrick from Sao Paulo-based Palmeiras in 2022, with a view to him joining Madrid in July 2024 after turning 18.
Spanish media reported that Endrick, who will wear Real's number 16 jersey, was signed for an initial fee of 35 million euros ($38 million) with a further 25 million euros in possible add-ons.
"This is crazy! I'm so happy, since I was a kid I have always been a Madrid fan and now I am going to play for Madrid," Endrick said at his presentation ceremony.
"I don't have words to describe what I am feeling. I always wanted to be here. I wanted to play for Madrid. It was a dream. Today it is a reality."
A product of the Palmeiras academy, Endrick has scored three goals in 10 appearances for Brazil since his debut last year and is the youngest male player to score an international goal at Wembley.
He scored 21 times in 82 Palmeiras games.
