Jieznas was first mentioned in written sources in 1492 as property of the Grand Duke of Lithuania. In 1633, the settlement was acquired by the Pac family. They sponsored construction of a church, which was reconstructed in Baroque style in 1768–1772.
In 1747, the Pac family built a luxurious palace in Jieznas. The palace had 12 halls, 52 rooms, and 365 windows to match the number of months, weeks, and days in a year. It was decorated with frescoes, gilded engravings, Venetian mirrors. The palace was lost due to family indebtedness in 1807 and was destroyed by a fire in 1837.
In February 1919, Jieznas saw the first battles and casualties of the Lithuanian–Soviet War. Lithuanian victory prevented the Red Army from marching into Kaunas. This battle is commemorated by the coat or arms, designed by Arvydas Každailis in 2002. The coat of arms depicts allegorical figure of a woman symbolizing the victory. She holds a golden oak branch, a symbol of strength.
^ abcSemaška, Algimantas (2006). Kelionių vadovas po Lietuvą: 1000 lankytinų vietovių norintiems geriau pažinti gimtąjį kraštą (in Lithuanian) (4th ed. ed.). Vilnius: Algimantas. p. 286. ISBN9986-509-90-4.