After the resignation of Jouthe, he was appointed interim prime minister by President Jovenel Moïse on 14 April 2021. Moïse chose Ariel Henry to succeed him in this role, but did not sign Henry's appointment. On 7 July 2021, President Moïse was assassinated and
First Lady Martine Moïse was injured during an attack at their residence in
Pétion-Ville. Joseph assumed political control of the government, At that time, Joseph stated that he was in control of the country. The legal succession to the presidency was unclear. Meanwhile, eight out of ten sitting members of Haiti's
Senate chose the Senate speaker
Joseph Lambert as the interim President on 9 July. The United Nations special envoy for Haiti,
Helen La Lime, said on 8 July 2021 that Joseph would lead Haiti until an election is held later in the year, urging all parties to set aside differences. The United States meanwhile recognized Joseph as the interim Prime Minister of Haiti. A group of prominent diplomats to Haiti called the "Core Group", which is made up of ambassadors to Haiti from Brazil, the European Union, France, Germany, Spain and the United States, in addition to representatives to Haiti from the
Organization of American States and the United Nations, called on Ariel Henry to take charge as the head of the government. On 19 July, Joseph announced in an interview with
The Washington Post that he would be stepping down soon and handing over power to Henry, whom he had met with many times in the past week to resolve the dispute, but expected that he will remain the foreign minister in that government. He added that he was doing it to honor the late President Moïse's final wish. Upon being questioned by
The New York Times, he rejected that he was stepping down due to international pressure. Henry was sworn in on 20 July, while Joseph retained the post of foreign minister. ==Post-premiership==