The SPD's Olaf Scholz is due to be elected chancellor by the Bundestag lower house of parliament and officially take office on Wednesday.
Germany's incoming governing parties have signed their agreement for what they portray as a progressive coalition.
The deal on Tuesday came a day before Olaf Scholz is due to succeed longtime leader Angela Merkel as chancellor.
The agreement hammered out last month between Scholz's centre-left Social Democrats, the environmentalist Greens, and the pro-business Free Democrats received strong backing over recent days from the three parties' members.
That has cleared the way for Scholz to be elected on Wednesday in parliament, where the coalition — which has never yet been tried in a national government — has a solid majority.
The 177-page coalition agreement is titled “Venture More Progress” — a theme that the incoming government's leaders hammered home at a signing ceremony at Berlin's Futurium museum.
Efforts to curb climate change are a top priority for the new government, particularly the Greens. Other priorities include modernizing Europe’s biggest economy and introducing more liberal social policies. Above all, though, the government faces the immediate task of pushing down near-record coronavirus infection rates.
The agreement between three parties that had significant differences before Germany's September election was reached relatively quickly and, at least in public, in unexpected harmony.