Jean-Bertrand Aristide's plane touched down in Haiti on Friday, ending the former president's seven-year exile.
"There's a real excitement because people have been talking about Aristide coming back for years now," the CBC's Connie Watson reported from Port-au-Prince.
Aristide was exiled to South Africa in 2004 after fleeing a rebellion.
He was Haiti's first democratically elected president, but was ousted in a coup, then restored to power in a U.S. military intervention in 1994.
He remains wildly popular among the country's majority poor.
Slams banning of party
Aristide has pledged to live as a private citizen in Haiti, though many are concerned he may try to influence the country's political landscape.
Shortly after arriving Friday, he slammed the barring of his political party, Lavalas, from Sunday's presidential runoff election, calling it "the exclusion of the majority."
Fears that Aristide would interfere in Haitian politics have prompted international expressions of concern.
U.S. President Barack Obama had urged the South African government to delay Aristide's return until after the election.
"The United States is saying if Aristide really didn't want to mess in the election, why was he so obsessed with coming before the vote on Sunday?" Watson reported. "There are people wondering if he has ulterior motives."
But the former president's aides say the successful presidential candidate could have barred Aristide's return had he waited.
South African officials also said they were not sending Aristide — who has held a Haitian diplomatic passport since February — to Haiti but were merely allowing him to leave the country.
The Associated Press reported that an endorsement from Aristide could turn the tide in favour of either presidential candidate.