Moïse called Preval a "worthy son of Haiti." He did not say how Preval died.
The former President died at his home in Laboule, a suburb of the capital city of Port-au-Prince, Haiti's daily newspaper, Le Nouvelliste, reported.
Preval was President of the Caribbean nation from 1996 to 2001 and from 2006 to 2011.
He was the nation's leader when a major earthquake killed more than 200,000 people in 2010.
Preval was born in Port-au-Prince in 1943. His father was an agronomist -- someone who studies crop production and soil management -- and Preval went to Belgium as a college student to study the subject.
He also studied in Italy before moving to Brooklyn, New York, in 1970 and spending five years there working as a waiter and messenger, according to Britannica.com.
He returned to Haiti and in 1990 he was appointed prime minister by President Jean-Bertrand Aristide. But in September 1991 the two fled after a military coup. Three years later the United States sent troops to Haiti and Aristide reclaimed power a month later.
Preval succeeded Aristide, with Preval finishing his first term in 2001. Re-elected in 2006, he became the first democratically elected president to serve a full term in the country, known for political turmoil. He won the support of much of Haiti's poor by achieving some land reform and running a government relatively free of corruption.
Preval returned to the office in 2006, once again following Aristide, but the two men were no longer political allies. Aristide, in fact had fled the country again in 2004.
Preval again served a full five-year term until Michel Martelly took office in 2011,
"President Préval, Ti René, my brother, my friend and adviser, your departure leaves us shocked," Martelly tweeted Friday.