The Social Democratic Party picked the contender from three candidates - Gintautas Paluckas, Egidijus Gaidamavičius and Rimantas Vaitkus.
Prime Minister, Chair of the party Algirdas Butkevičius had endorsed Paluckas, 35, and urged to put forward and support young people.
Municipal elections, where people will elect mayors in direct vote for the first time, are scheduled for 1 March 2015.
The nominee of the Liberal Movement for Vilnius mayor is former justice minister, MP Remigijus Šimašius. The conservative Homeland Union intends to nominate non-partisan former finance minister Ingrida Šimonytė.