Its administrative seat and largest town is Marijampolė.

Marijampolė Municipality was established in 2000 after the territorial administrative reform, which abolished the Marijampolė District Municipality.

The members of the City Council represent different Lithuanian political parties.

They are: Gudeliai, Igliauka, Liudvinavas, Marijampolė, Sasnava, and Šunskai communities.

Marijampolė Municipality covers 755 square kilometres (292 sq mi) of land; 72% of which is an agricultural area, 12.3% is covered by forests; 4.2% – towns and villages, 2% – industrial enterprises and roads, and 6.9% – area used for other purposes.