The German club have secured an option to buy 28-year-old Arias when his loan term ends next year.
— Bayer 04 Leverkusen (@bayer04_en) September 24, 2020
53-time Colombian international Arias joined Atleti from PSV in 2018 for around €11m.
His performances for Diego Simeone’s side were good, but he found starts harder to come by in his second year at the Madrid club.
Right-back Arias said he is looking forward to a new challenge in Germany.
“A fantastic opportunity to take on a new challenge after two great and successful years in Madrid,” he said. “Bayer 04 Leverkusen are one of the best clubs in the Bundesliga with a very good reputation in Spain.
“I experienced how football’s played here with Atlético in the Champions League. That’s why I’m very much looking forward to the German league and my new teammates. We have a team that can go a long way – and I want to help achieve that.”