"To be a part of such a big club makes me proud," Jota told Atletico's official website (www.clubatleticodemadrid.com).
"It is a great club at all levels and I didn't think twice about accepting this offer.
"I want to fight to establish myself in the club. It will be a season of learning. I hope to be in the plans of the coach."
Atletico did not reveal any financial details of the deal but Spanish media estimated the transfer fee for the Portuguese under-21 international to be in the region of 7 million euros (6 million pounds).
The Spanish side's sporting director Jose Luis Perez Caminero believes Jota will be a great addition to his club.
"He is a young player, very fast and upright, carries the ball very well and has great acceleration," Caminero said.
"Diogo has a great future and stands out for his one-on-one technique and his versatility, because he can play in several positions."
Jota will join up with his new team for pre-season training on Thursday.
($1 = 0.9038 euros)
(Reporting by Adriana Garcia; Editing by John O'Brien)
