Manchester City were playing their first competitive game without Pep Guardiola as their manager in over 10 years, since Manuel Pellegrini oversaw a 1-1 draw with Swansea in May, 2016.
New manager Enzo Maresca gave £116m signing Elliot Anderson his competitive City debut and started Phil Foden, who had been out of favour under Guardiola last season.
Jack Grealish also came on in the second half for his first City appearance in 15 months.
City were unable to match Arsenal's physicality but did test goalkeeper David Raya numerous times, with the Spaniard doing well to keep out low, driven shots from Foden and Antoine Semenyo.
Their defeat was the biggest in the Community Shield since 2014, when Arsene Wenger's Arsenal also beat Pellegrini's City 3-0.