The moves were prompted by the nomination of Macron's ultra-loyal government spokesman, Christophe Castaner, as head of his Republic on the Move (LREM) party last Saturday.
Olivier Dussopt, a 39-year-old specialist in regional affairs, will become junior minister in the public accounts ministry led by Gerard Darmanin.
Dussopt -- who voted against Macron's 2018 budget in a National Assembly vote just a few days ago -- will oversee finances for France's public sector, which Macron has vowed to pare down.
The budget puts a freeze on major infrastructure projects, while nearly 1,600 civil service jobs are to be axed.
Dussopt's nomination did not go over well with his leftist colleagues, with one party official, Rachid Temal, telling AFP that "He is no longer a Socialist Party member."
Another new arrival in the government is Delphine Geny-Stephann, 49, who had been a high-ranking finance ministry official until 2005, when she joined the French glass and building materials group Saint-Gobain.
She was named junior finance minister. Her boss Bruno Le Maire said this week that Macron was "totally determined" to bring France's deficit below the EU limit of three percent of GDP this year.
Benjamin Griveaux, the junior finance minister who was the spokesman for Macron's En Marche (On the Move) movement before he was swept to the presidency in May, will become the government's spokesman.
Macron has been moving to rekindle the support of his base after passing labour overhauls and tax cuts that trade unionists and even his leftwing supporters say favour businesses and the wealthy.
Last Saturday, hundreds of protesters marched to Macron's official residence in Paris to denounce what they called his "anti-social policies".
By Laurence Benhamou and Jérôme Rivet