President Joseph Kabila and his four new deputies are to lead the vast central African country into its first elections since independence in 1960.
But even as they vowed to respect the April peace accord, the DRC's new constitution and the unity of the country, violence still rocked the north-eastern Ituri and the eastern Kivu provinces.
More than 3,000 people gathered in the vast hall of the People's Palace in the DRC capital Kinshasa for the investitures.
The crowd included ministers of the transition government who will take office on Saturday, as well as hundreds of legislators and senators.
The biggest accolade was reserved for Jean-Pierre Bemba, head of the former rebel Congolese Liberation Movement (MLC).
The other three were Azarias Ruberwa of the former rebel Congolese Rally for Democracy, Abdoulaye Yerodia Ndombasi of the outgoing Kinshasa regime, and Arthur Zahidi Ngoma of the political opposition.
A murmur went up during the swearing-in of 38-year-old Ruberwa of the Rwandan-backed Congolese Rally for Democracy (RCD) when he pledged to honour the "unity and indivisibility" of the DRC.
The RCD controlled a large swathe of the east of the country through most of the war and was considered the most recalcitrant of the belligerent sides through a series of failed peace summits.
The RCD's seven ministers and four deputy ministers as well as Ruberwa himself were the last members of the new government to arrive in Kinshasa for the ceremonies, each demanding 15 bodyguards before they came.
The four include the leaders of two rebel groups which launched a bid in August 1998 to topple the government of Laurent Kabila, the father of the current president Joseph Kabila. Laurent was eventually assassinated.
Both rebellions were backed by neighbouring Rwanda and Uganda, while four other countries -- Angola, Zimbabwe, Namibia and Chad -- backed the Kabila government. This became known as "Africa's world war," a conflict that has claimed more than 2.5 million lives through combat or disease and starvation.