Costa has exiled himself from the Chelsea team and spent the last few months in his hometown of Lagarto in Brazil.
The striker has refused to report for training since he received a text message from Antonio Conte stating that he is no longer part of his plans.
But according to the Spanish publication, the ugly feud has now come to an end and Costa has returned to Chelsea.
The Spain international is, however, still trying to force his way out of the club and will hold talks with Chelsea chiefs with the view of leaving the club in January.
Atletico are very interested in a deal to bring their former talisman back to Madrid and were locked in negotiations with Chelsea towards the end of this summer's transfer window but failed to come to an agreement.
The Spanish side have played a part in Costa's return as they encouraged him to make peace with Conte as they eye a January transfer.
Costa has been included in the Blues Premier League squad, but didn't make the cut for the Champions League.
Will the striker force through a move in the new year?