The FDP was the second party to approve the coalition agreement.
The delegates at an extraordinary federal party conference on Sunday voted 92.2 percent for the adoption of the 177-page paper for future government work with the SPD and the Greens.
The FDP chairman Christian Lindner had previously campaigned for approval for the coalition agreement in his speech.
"It is a coalition agreement for a policy of the center that does not move our country to the left, but wants to lead it forward," said Lindner in Berlin.
Among other things, he emphasized that the contract contained the renewal of the liberal promises of education and promotion.
In addition, he stands for a socio-political awakening, provides solid finances and includes the digitization of state and society.
On Saturday, more than 98 percent of the delegates approved at an SPD party congress.
The result of the strike vote among the Greens is expected this Monday.
The coalition agreement is due to be signed on Tuesday.
More information soon on FAZ.NET.