After a meeting of military leaders and top government officials, President Dalia Grybauskaite said today the measure was necessary because of "growing aggression" in Ukraine.
Military officials said Lithuania will reinstate national service for five years starting in September, when it will enlist some 3,000 men, ages 19 to 27. They will serve for nine months.
Gen Jonas Vytautas, the defense chief, says a lack of soldiers posed a "real threat" to national security.
Lithuania, like its Baltic neighbours Latvia and Estonia, was occupied for five decades by the Soviet Union before regaining independence in 1991. It abolished conscription in 2008, four years after joining NATO.