The Asian champions' results in Group A, which also contains the Republic of Ireland, Serbia, Azerbaijan and Luxembourg, will not count towards qualification as they are already assured of a place in the finals given their status as hosts.
They will face each side twice, but their 'home' matches will be staged in Europe to allow shorter flight times for their opponents.
It is hoped that Qatar, who are also set to play in the Copa America and Gold Cup next year, will gain further experience from competing against European nations such as Cristiano Ronaldo's Portugal.
UEFA confirmed the news on Tuesday and announced Qatar would begin their campaign against Luxembourg at a neutral venue yet to be confirmed on March 24, 2021.
Felix Sanchez Bas' side, who are ranked 59th in the world and won their first ever Asian Cup with a 3-1 win over Japan in last year's final, will take on Portugal next September and October.