Costa was officially presented at the Wanda Metropolitano stadium on Sunday, alongside fellow Spain team mate Vitolo, who signed from Sevilla in July.
Atletico Madrid manager Diego Simeone expressed his great pleasure and satisfaction to be in Egypt to take part in a friendly match for a great cause like peace and anti-terrorism against the Egyptian giant Al Ahly.
The Premier League champions announced in September that they had reached an agreement with Atletico over the return of Costa.
"I've been waiting for this moment for a long time, I just want to get in shape to play as soon as possible".
"I want to thank the club for all the hard work they did to be able to bring me back", he said at the unveiling ceremony. "That shows that I have worked and I have prepared well to play, I come here to help the team and score goals".More news: Tune in tomorrow for President Buhari's New Year Address
I didn't learn English, which is a bit of a shame. "The people ahead of me are doing well".
Antoine Griezmann is Atletico's leading marksman with five league goals but Costa will have to prove his fitness as his last competitive game was for Spain in a World Cup qualifier against Macedonia on June 11.
The striker left the Spanish capital club in 2014 for Stamford Bridge, winning two Premier League titles before heading back.
"I was very well, the people, the fans, the teammates have helped me a lot".
"I have a special affection for them, I only have good memories". "Chelsea is a great club", he added.