Joseph was appointed interim Prime Minister following the resignation of Joseph Jouthe. After the assassination of President Jovenel Moïse on 7 July 2021, Joseph assumed the office of acting President and was internationally recognized as such. As he was not a confirmed Prime Minister, the legality of his succession was unclear and disputed by Prime Minister-designate Ariel Henry and Senate leader Joseph Lambert. Joseph had announced his intention to hold the 2021 Haitian general election in September as scheduled. On 19 July 2021, under a subsequent political agreement, it was announced Joseph will yield the prime ministership to Henry and will remain the Minister of Foreign Affairs and Worship.