A approval from SPD's over 358,000 members means that the way is open for CDU leader Friedrich Merz to become Germany's new Federal Chancellor. The coalition has previously been approved by the Christian Democratic CDU and its sister party CSU.
The Parliament will meet on Tuesday to elect Merz, who will need a majority of votes in the lower house to succeed Social Democrat Olaf Scholz.
56 percent of SPD's members voted on the coalition, 84.6 percent of them voted in favor, the party announced.
CDU/CSU became the largest in the election with 28.6 percent of the votes, but not large enough to get their own majority, and were therefore forced to enter into coalition negotiations. The agreement on the coalition between CDU/CSU and SPD was presented a couple of weeks after the election.
The coalition gets a relatively small majority with 328 of the 630 seats in the Bundestag.
