The Portuguese coach was spotted wearing a black baseball cap after taking his seat at the home of his local rivals, who are playing their second Premier League match of the season.
📷 | Mourinho at the Etihad. pic.twitter.com/DEuPQrad1D— Man Utd Stuff (@ManUtdStuff) August 21, 2017
Mourinho will not take on Pep Guardiola's men until December 9 when United host their neighbours at Old Trafford, but the Red Devils will face Everton in three weeks' time.
United have had a positive start to the season, winning by 4-0 in games against West Ham United and Swansea City.
United's legendary former manager Sir Alex Ferguson was also in attendance at the Etihad.