The Spanish youngster has agreed to join the Bundesliga outfit on a permanent deal after failing to make the breakthrough at the Santiago Bernabeu
Goal.com had exclusively revealed last week that the 20-year-old was poised to sign for the Bundesliga giants, and the right-back has now declared that he has completed a transfer to the BayArena side.
It is believed Carvajal will cost Leverkusen €5 million (£3.9m), with the former Spain Under-19 international hinting that Madrid have included a buy-back clause in the deal.
"Today I made an important step in my career, I am now a player of Leverkusen for the next five seasons," Carvajal wrote on his Twitter page.
"I hope to improve as a player and be able to return to Madrid in the future, when I am ready to be a part of their first team."
Carvajal, a product of Madrid's youth ranks, had been tipped to break into Madrid's senior squad next season to provide cover for Alvaro Arbeloa.
Former defender Michel Salgado recently backed the youngster to become Los Blancos' first-choice right-back in the space of two years.