The 20-year-old Brazilian striker agreed the switch to the Vicente Calderon on a five-year contract from Rayo Vallecano last month, and officially became an Atletico player when the transfer window opened on July 1.
Speaking at his presentation, he was quoted as saying by Spanish newspaper Marca: "Today is an important day for me. I am very excited to have signed for Atletico Madrid.
"It's a dream to play in a great team with great quality.
"It is a dream come true. For a boy of 20 years, this has happened to me very fast: the debut, goals, and move to a big team.
"I come eager to learn and to win. I'm very young and I will bring a lot to the club."
He added: "I do not think about the pressure. I'm very young and I will learn a lot at this club."
Baptistao scored seven goals in 28 league appearances for Rayo in the 2012-13 campaign, playing his part as Atletico's city rivals secured eighth place in the Primera Division table.