Friday's swearing-in ceremony was the final step in transferring power from a two-year-old interim government installed after Jean-Bertrand Aristide, the former president, left the Caribbean nation for exile in Africa amid a February 2004 revolt.
President Rene Preval said the 18-member cabinet made up of members from six political parties was the result of a new "spirit of dialogue," and urged Haitians to work together to overcome the "mistrust" among Haiti's deeply divided political factions.
In a speech at the National Palace, Preval said: "We are on the path to recovering our dignity and sovereignty. The dialogue has begun and the dialogue will continue, but I need everyone's help."
Preval, 63, took power last month and has said national unity is vital to restoring security and allowing the withdrawal of a Brazil-led UN peacekeeping force sent to quell violence in the aftermath of the uprising.
Friday's ceremony was attended by the new cabinet, outgoing interim ministers and foreign diplomats. Noticeably absent was Gerard Latortue, the ex-interim prime minister, who left the country for the US last month for personal reasons.
The new cabinet includes several members of Preval's Lespwa party and a representative from five other parties, including Aristide's Fanmi Lavalas.
Preval urged the ministers not to replace "serious-minded" civil servants hired by the interim government, which he called an error of successive administrations over the past 20 years.
"Let us not repeat the mistakes of the past," Preval said. "Reinforcing the state does not mean engaging in the dangerous exercise of throwing out civil servants."
The cabinet was appointed earlier this week and formally approved by parliament on Wednesday. It will be led by Jacques-Edouard Alexis, the prime minister, who also formally took office on Thursday.
Alexis, 58, served as prime minister for two years during Preval's 1996-2001 presidency and is seen as someone with the political clout needed to hold sway in Haiti's fractured parliament, where no party holds a majority.