The two agencies pitched for the business together against Krow, Iris and the Glasgow-based agency Frame, the incumbent on the account. The pitch began in March and was handled by the AAR.
McCann will now be responsible for Subway's TV advertising, while Momentum has point-of-sale and digital duties.
The Subway franchises currently pay a percentage of their turnover to a communications fund, which is split on a regional and national basis. Separate regional and national boards then decide how to spend the money.
Frame picked up Subway's regional business in July 2005 and was appointed to the national account in September of the same year. It was responsible for the global sandwich chain's "Sub of the Day" positioning.