Mohammed al Bashir said in a televised statement on Tuesday that he had been appointed caretaker prime minister of the transitional Syrian government until March 1, 2025.
Al Bashir ran the opposition-led Salvation Government before the 12-day lightning offensive swept into Damascus.
Members of the Syrian regime under ousted Bashar al Assad will gradually transfer power to a new transitional cabinet.
The outgoing regime officials met with Bashir for the first time since Assad fled Damascus over the weekend.
Bashir told reporters after the meeting that the ministers discussed transferring the portfolios to the interim government during the transitional period.
He said that in the coming days, the new government will decide on each ministry.
Separately, Qatari officials made their first contact with the newly announced transitional government representatives, an official briefed on the developments told AFP.
"Qatari diplomats are expected to continue in the next 24 hours with al Bashir," the official said on condition of anonymity.