The storm brought winds of up to 200 kilometres per hour, pounding coastal villages and forcing many to flee their flooded homes.
The scale of the damage and casualties is not yet known, but Haiti's interim president says some people who had not, as he puts it, "respected alerts" had died.
The most powerful Caribbean hurricane in nearly a decade has hit the country perhaps least able to withstand it.
Haiti, one of the world's poorest countries, is still recovering from a 2010 earthquake that killed more than 200,000 people, as well as a cholera epidemic that followed.
Save the Children's country director in Haiti, Kevin Novotny, says, while the full scale of the damage is still being assessed, it is clearly a huge setback for the country.
"I think we've probably gone back about a year, a year and a half, in progress, just overnight, if you look at the damage, particularly along the south, along the infrastructure, the roads, the schools, the clinics, the communications, you know, major bridges out, from my understanding, going to the south. So, from an infrastructure and development perspective, yes, I think we've gone backwards."
Mr Novotny points out many of Haiti's 11 million residents live in homes that are already flimsy and prone to flooding.
"Many of the houses, particularly along the coast, you'll have a lot of houses that have either palm frond or tin roof, tin sheet roofing, concrete walls in most cases. In other cases, wood. So certainly not built to withstand 140 mile an hour winds."
However, he says, many people refused to evacuate, fearing they might lose the few possessions they have.
"I think people often, in a particular area like that, where you don't have much, you'd rather stay and try to protect it than run away from it. Looting might not be as big of an issue as the fact of just fearing that they'll come back to nothing."
Local television and radio journalist Brunelli Sester-Joseph has told the BBC others may have stayed in their homes because of their religious faith, along with the vandalism fears.
"They were very reluctant. It took the last minute, the very last minute, when they were knee-deep in mud and water, to evacuate. The number one fear, of course, is vandalism. They do not want to leave their property, because they fear that people will take that time to vandalise their homes. And, secondly, is faith, that 'Bondye pa bòpè' expression which means, 'God is good, therefore, this will not happen.' It's almost a disbelief of that actual storm coming at them."
The spread of cholera will again be a major concern after the hurricane caused widespread flooding, along with the spread of Zika and mosquito-borne diseases
CARE Australia's country director in Haiti, Jean-Michel Vigreux says there are also concerns for children who have been separated from their families.
"We heard already that children came to shelter with no relatives, no parents, no adults. So that means that there are definitely families that have been separated, whose members have been separated. And we will have to reconnect the children with their parents as quickly as possible."
Mr Vigreux says the latest disaster highlights the need for long-term solutions in Haiti.
"We need to always work within the perspective that there will always be recurring shocks. And, therefore, it's better to really transform the capacity of the population to be able to cope with those shocks. There's nothing we can do about the disasters themselves -- it's a natural phenomenon -- but we can certainly prepare the population to be much more resilient."
