Founded in Břevnov atop earlier social democratic initiatives, such as the Ouls, it represented much of the Kingdom of Bohemia in the Austrian parliament, and its significant role in the political life of the empire was one of the factors that led to the creation of an independent Czechoslovakia.

During the occupation of the Czech lands by Nazi Germany, the party was officially abolished, but its members organized resistance movements contrary to the laws of the German-controlled Protectorate of Bohemia and Moravia, both at home and abroad.

After the re-establishment of the Czechoslovak Republic in 1945, the party returned to its pre-war structure and became a member of the National Front which formed a new governing coalition.

At the time of the Prague Spring, a reformist movement in 1968, there were talks about allowing the recreation of a social democratic party, but Soviet intervention put an end to such ideas.

The successor of Gross as prime minister was Jiří Paroubek, while Bohuslav Sobotka became acting party leader from 26 April 2005 to 13 May 2006.

[13] The party suffered heavy losses in the 2017 Czech legislative election and was reduced to 15 seats, the worst result in its history.

Party chair Jan Hamáček resigned on the election day, as some high-ranking members blamed ANO for the lost.

[17] Later that year, Mayor of the Nové Město na Moravě Michal Šmarda defeated former Minister of Labor Jana Maláčová in the leadership contest,[18] vowing to return the party to Parliament.

[21] He also says he sees the party back at a 30% vote share in four years and at 10% in the next parliamentary election,[22] claiming that under his leadership, SOCDEM will not form a government with ANO, ODS, TOP 09, SPD or KSČM.

Šmarda refused to support any other candidate, but called on his fellow party members to vote against Andrej Babiš, Jaroslav Bašta and Karel Diviš.

The party had chosen to run independently, after coalition talks with the Greens failed,[25] but opted to invite Budoucnost members on its list.

[26] SOCDEM received 1.86% of the vote share at the election, failing to enter the European Parliament for the second consecutive time, and finishing 9th overall.