The 63-year-old agronomist was sworn in Sunday at a ceremony that drew thousands to the National Palace and marked the return of democratic rule to Haiti.
Preval has worked to keep expectations low and has asked for the patience of Haitians, particularly the poor who came out in droves to elect him in February.
During a recent visit to the United Nations, he asked donor nations that have helped keep Haiti afloat to make a 25-year commitment. An international donor conference has been set for July, according to the Washington Post.
He also traveled to Venezuela and Cuba, which have strained relations with the United States, and brokered an oil deal with Venezuelan President Hugo Chavez.
A Venezuelan oil freighter sat offshore to make the first delivery Sunday, the Post reported.
Preval, who governed Haiti from 1996 to 2001, replaces a U.S.-backed interim government appointed after a bloody revolt pushed Jean-Bertrand Aristide from power in February 2004.
Thousands cheered Preval on Sunday, pressing against the palace gates and waving Haitian flags as dozens of U.N. peacekeepers stood guard.
About 300 legislators and foreign dignitaries, including Florida Gov. Jeb Bush, Canadian Gov. Gen. Michaelle Jean and actor Danny Glover, gave him a standing ovation, according to the Associated Press.
Preval urged Haitians to maintain security so the country could create jobs, build roads and hospitals and move forward "without the presence of foreign troops," reported the AP.
"Haitian people, the solution to our problems is in our hands," he said. "Please help me, help the country, help yourself."
He paid tribute to outgoing officials, including Prime Minister Gerard Latortue and President Boniface Alexandre, in his 10-minute inaugural address.
Since Preval's Lespwa Party failed to win a majority of seats in parliamentary elections, Preval must form a unity government with rival parties.