The Uruguay international signed a two-year contract with the club after passing his medical.
The 33-year-old senior forward had joined Barca from Liverpool in 2014.
He ended up scoring 198 goals in 283 appearances for the club.
Here are further details on Suarez's transfer.
Barcelona paid £74m to sign Suarez from Liverpool but Ronald Koeman told him last month that he was not in his plans.
This led to Suarez agreeing a deal with Italian champions Juventus but the deal fell through because of passport issues.
Atletico decided to pay a nominal fee of no more than 6m euros as Suarez agreed terms on a reduced salary.
Juve will pay Atletico £9.2m for Morata's services this season.
Morata had joined Atletico on loan from the Blues in January 2019 on an 18-month loan deal.
He ended up with 22 goals from 61 games for the side.
Since joining Barcelona in 2014, Suarez went on to make his presence felt after delivering consistently.
He scored 198 goals in 293 appearances for Barca during his six-year stay.
The prolific forward netted 147 La Liga goals in 191 games.
He won 13 trophies, including four La Liga honors and one Champions League.
Lionel Messi lashed out at Barcelona and said Suarez deserved a better send-off from them.
"You deserved a send-off matching who you are - one of the most important players in the club's history, achieving important things both as a group and individually," he said.
"Not to get thrown out like you have been. But the truth is at this point nothing surprises me."
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