The La Liga Feminina champions have locked in the 20-year old after she accepted a two-year deal which will keep her in the Spanish capital until 2021.
The news is sure to provide some consolation for the midfielder after she narrowly missed a spot in the Matildas 23-player FIFA Women's World Cup squad.
Chidiac said she looks forward to trying to repay Atleti's faith next season with a bigger contribution on the field.
"I am very happy that Atlético believes in me to extend my contract and be an integral part of this team," she said.
"Being part of a club with so much history and professionalism has given me an incredible first experience abroad."
The former W-League player with Adelaide United and Melbourne City made 19 appearances for Atleti this season as the club clinched their third straight league title.
Chidiac also found the back of the net three times this campaign.
