The vote is the first time a Linke politician has been elected to lead a state government since the party evolved from the ashes of the Socialist Unity Party (the SED), which led East Germany for most of its existence.
Thuringia will be governed by a narrow majority government composed of the Linke, the Social Democrats (SPD) and the Green party.
They lead while holding 46 of the 90 parliamentary seats in the state senate.
Voting was tense on Friday, as the first round of voting failed to get Ramelow sworn in as one representative among the coalition members abstained. In the second round, all coalition seats voted for the 58-year-old former trade unionist.
"We are deciding the political culture of our state," Ramelow said upon his electiong, promising that the state chancellery will remain an "open house" for his political rivals.
The election of a Linke minister-president was met with much resistance outside the house. On Thursday, around 2,000 people protested the expected results of the state parliament in Erfurt. People held signs saying: "Rescue Thuringia from blood-red, red and green."
In November, 4,000 people marched in a demonstration against the coalition plan to put the Linke politician in charge, mimicking the Monday demonstrations of 1989 that eventually led to the collapse of the East German state.
There, people carried signs accusing the SPD of betrayal for their agreement with the Linke while chanting "Stasi out!", referring to the brutal state police of the East German regime
The director of the Stasi memorial in Berlin said that many victims of the SED government are stunned by the news.
"They feel that the lessons in history are being forgotten. They worry that politicians who were ousted 25 years ago are going to make comebacks," Hubertus Knabe told the Nordwest-Zeitung, adding that for many of those he represents, the Linke are no better than the SED.
"More than two-thirds of the party members are fomer SED comrades," he said.
Even German president Wolfgang Gauck spoke out from his traditionally neutral office and said he found "it quite hard to accept this". Gauck was a dissident Lutheran pastor in East Germany in the 1980s.
Prior to Thursday's vote, the Christian Democrats (CDU) led the state for 24 years and had won the largest portion of the September vote, though could not cobble together a governing majority. They refused to work with the anti-EU upstart Alternative for Germany (AfD) politicians.
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