كتب : Omar AbdelAziz
Reyes passed a medical at Vicente Calderon before signing a four-year deal with the Spanish Primera Liga side.
The 23-year-old, who spent the previous season on loan at Real Madrid, was poised to a move to one of the two Madrid rivals, but Atletico's $12 million bid excelled Real $8million offer.
Reyes scored six Primera Liga goals for Los Blancos last season, including a crucial equalizer in Real's final day 3-1 win over Mallorca, which handed them the title.
The former Sevilla winger has won 21 caps for the Spanish national team so far.