[6] Initial discussions about forming a Marxist political party in Lithuania began early in 1895, with a number of informal gatherings bringing together social democrats of various stripes resulting in a preparatory conference in the summer of that year.

[10] Among the 13 delegates were Andrius Domaševičius and Alfonsas Moravskis—a pair of intellectuals regarded as the central organisers of the new political entity—and the future President of Lithuania, Kazys Grinius, as well as a number of worker activists.

[11] Also in attendance as a representative of the radical youth movement was an 18-year-old ethnic Pole named Felix Dzerzhinsky, later the head of the Soviet secret police.

[10] As Lithuania was then part of the Russian Empire, the LSDP was inevitably an illegal organisation, meeting in secret and seeking to bring about the revolutionary overthrow of the Tsarist regime.

[13] Technical assistance was occasionally provided by the Social Democracy of the Kingdom of Poland and Lithuania party, headed by Julian Marchlewski.

[14] Approximately 280 socialist and trade union organisers were apprehended during this period, with subsequent trials leading to the Siberian exile of more than 40 people, including Domaševičius and Dzerzhinsky.

[14] Other top leaders, including Moravskis, were forced to flee the country to avoid being swept up in the Okhrana's dragnet.

[14] With the party leadership jailed or chased from the country, the LSDP very nearly ceased to exist as the 19th century drew to a close.

[14] From 1900 to 1902, the Social Democratic Party of Lithuania began to tentatively rise from the ashes behind a new crop of young revolutionaries.

Butkevičius became the prime minister, forming a coalition government with the Labour Party, Order and Justice and Electoral Action of Poles in Lithuania – Christian Families Alliance.

[19] At the 2016 parliamentary elections, the party took 21 seats and formed a coalition with Lithuanian Farmers and Greens Union.

[20] In the 2024 parliamentary elections, the party achieved a "historic victory",[21] finishing in first place with 19.32% of the popular vote and 52 out of 141 seats.

The founder of Dawn of Nemunas, Remigijus Žemaitaitis, is known for making antisemitic statements,[24] and his party's inclusion sparked backlash from Lithuanian civil society groups,[25] as well as from lawmakers and ambassadors abroad, including US Senate Foreign Relations Committee chair Ben Cardin,[26] German MPs Roderich Kiesewetter and Michael Roth,[27] Polish senator Michał Kamiński,[28] and the Israeli embassy.

[27] However, no official PES condemnation of the coalition was issued, and the European party congratulated the Social Democrats with the formation of the Paluckas Cabinet on December 12.

According to political scientist Ainė Ramonaitė [lt], "before their split, the Social Democrats never managed to be a left-wing party.

"[33] During the Eleventh Seimas from 2012 to 2016, when the party played a leading role in the Butkevičius Cabinet, it was criticized by left-wing intellectuals such as Andrius Bielskis and Arkadijus Vinokuras for lacking allegiance to left-wing ideas and for its neoliberal policies, such as reforms to the Labour Code in 2016 which strengthened the position of employers in workplace relations.

[37] However, this renewal was also criticized as incomplete and straddling the fence between progressiveness and the party's previous non-ideological populism.

[43][44] By the end of decade, LSDP increased their support in Radviliškis District Municipality (probably, at expense of Democratic Labour Party of Lithuania (LDDP)).