The municipality's flag consists of two diagonally divided red and white pennons.

The flag was ultimately derived from the corresponding municipal coat of arms.

[1] The flag of Utrecht originates from the medieval period, during which the city's militia was divided into two factions each symbolised by a single white and a single red monochromatic, triangular pennant.

[2][3] The municipality's contemporary flag represents the merger of these two pennants and adheres to a proportion of 2:3.

[4] Historically, flags prominently featured Saint Martin, the municipality's patron saint, depicted on horseback cutting his red cloak to give to an individual in need.