Antoine Armand, who is 33 and a graduate of France's top administration school, will serve as finance minister and Jean-Noel Barrot will become foreign minister in a government composed largely of centrist and conservative parties, Alexis Kohler said from the Elysee Palace late on Saturday.
Sebastien Lecornu will stay on as defence minister, he added.
There are questions over how stable the new government will prove to be, and whether it will manage to push reform measures through parliament, analysts say, with the adoption of the 2025 budget a first, tough challenge.
The government, led by conservative Michel Barnier, the European Union's former Brexit negotiator, will face the tough task of having to plug a gaping hole in public finances, which could involve having to decide politically toxic tax rises.
Macron named Barnier, a 73-year-old veteran politician as prime minister earlier this month, but the lengthy talks he had to lead to pull together a team were an illustration of the tough tasks ahead.
The centrist and conservative parties managed to pull forces, but will depend on others, and in particular Marine Le Pen's far right National Rally (RN), to stay in power and get bills adopted by a very fractured parliament.
"The centrist government is de facto a minority administration," Eurointelligence analysts said in a note.Â
Its ministers "will not only have to agree amongst each other but also will need votes from opposition parties for its bills to pass in the assembly. This means offering even more concessions and manoeuvring."
The RN gave tacit support to Barnier's premiership, but reserved the right to back out at any point if its concerns over immigration, security and other issues were not met.
"I'm angry to see a government that looks set to recycle all the election losers," Mathilde Panot, who leads the hard-left LFI group of MPs, told TF1 television.
