Henry's finance minister, Michel Patrick Boisvert, will be interim prime minister until the transition council appoints a new head of government, a cabinet and a provisional electoral council set to pave the way for an eventual vote.
"Today is an important day in the life of our dear republic, this day in effect opens a view to a solution," Boisvert said after the formal swearing-in of the nine-person transition council on Thursday morning.
Even as the council was sworn in, local media reported houses being set on fire and shooting in capital Port-au-Prince's downtown and Delmas areas, posting photos of tall columns of grey smoke rising above the skyline.
Armed gangs, equipped with weapons trafficked largely from the United States, have for years tightened their grip on the capital and sought to topple Henry. Since he pledged to resign last month, they have called for a broader "revolution".
Earlier this week, gang leader Jimmy "Barbeque" Cherizier warned members of the transition council to "brace" themselves.
Unverified voice recordings circulated on social media over the weekend, which users attributed to Cherizier, in which Cherizier appeared to order his soldiers to indiscriminately burn houses in Lower Delmas, an impoverished part of the capital where he grew up.
At the ceremony, Boisvert and members of the transition council were flanked by top police and military officials. It was hosted amid tight security at the prime minister's office known as Villa d'Accueil.
Henry announced last month he would resign once the council was in place, initially expected to happen within a couple of days but delayed amid disagreements as to who should sit on it.
Henry had left Haiti in late February seeking support for the country's outgunned police, but was left stranded in Puerto Rico as the gangs threatened to completely take over the capital. Boisvert has served as acting prime minister in Henry's absence.
The transitional government's mandate runs until February 2026, by when there are slated to be elections, and cannot be renewed. No date has been set for its naming of a new prime minister or council president.
According to UN estimates, more than 2500 people were killed or injured in gang violence from January through March, while hundreds of thousands have been internally displaced and millions are facing catastrophic hunger.
Key ports have been closed for weeks, but on Thursday Florida-based non-profit Hope for Haiti said a first humanitarian flight since the capital's airport shut down over a month ago had landed in Port-au-Prince: a US military plane bringing 20 pallets of rehydration solution for cholera patients.
Countries in the region have bolstered border security and many have been deporting Haitians seeking to migrate abroad, despite UN criticisms.
